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15
README.md
Normal file
15
README.md
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@ -0,0 +1,15 @@
|
||||
optional
|
||||
========
|
||||
|
||||
A library for representing optional (nullable) objects in C++.
|
||||
|
||||
```cpp
|
||||
optional<int> readInt(); // this function may return either an int or a not-an-int
|
||||
|
||||
if (optional<int> oi = readInt()) // did I get a real int
|
||||
cout << "my int is: " << *oi; // use my int
|
||||
else
|
||||
cout << "I have no int";
|
||||
```
|
||||
|
||||
For more information refer to the documentation provided with this library.
|
||||
@ -10,6 +10,7 @@
|
||||
# Quickbook
|
||||
# -----------------------------------------------------------------------------
|
||||
|
||||
using boostbook ;
|
||||
import quickbook ;
|
||||
|
||||
path-constant images : html ;
|
||||
@ -24,7 +25,6 @@ boostbook standalone
|
||||
optional
|
||||
:
|
||||
<xsl:param>boost.root=../../../..
|
||||
<xsl:param>html.stylesheet=boostbook.css
|
||||
<xsl:param>toc.max.depth=2
|
||||
<xsl:param>toc.section.depth=2
|
||||
<xsl:param>chunk.section.depth=1
|
||||
|
||||
@ -14,4 +14,54 @@
|
||||
The implementation uses `type_traits/alignment_of.hpp` and
|
||||
`type_traits/type_with_alignment.hpp`
|
||||
|
||||
[section Optional Reference Binding]
|
||||
|
||||
On compilers that do not conform to Standard C++ rules of reference binding, operations on optional references might give adverse results: rather than binding a reference to a designated object they may create an unexpected temporary and bind to it. Compilers known to have these deficiencies include GCC versions 4.2, 4.3, 4.4, 4.5; QCC 4.4.2; MSVC versions 8.0, 9.0, 10.0, 11.0, 12.0. On these compilers prefer using direct-initialization and copy assignment of optional references to copy-initialization and assignment from `T&`:
|
||||
|
||||
const int i = 0;
|
||||
optional<const int&> or1;
|
||||
optional<const int&> or2 = i; // not portable
|
||||
or1 = i; // not portable
|
||||
|
||||
optional<const int&> or3(i); // portable
|
||||
or1 = optional<const int&>(i); // portable
|
||||
|
||||
In order to check if your compiler correctly implements reference binding use this test program.
|
||||
|
||||
#include <cassert>
|
||||
|
||||
const int global_i = 0;
|
||||
|
||||
struct TestingReferenceBinding
|
||||
{
|
||||
TestingReferenceBinding(const int& ii)
|
||||
{
|
||||
assert(&ii == &global_i);
|
||||
}
|
||||
|
||||
void operator=(const int& ii)
|
||||
{
|
||||
assert(&ii == &global_i);
|
||||
}
|
||||
|
||||
void operator=(int&&) // remove this if your compiler doesn't have rvalue refs
|
||||
{
|
||||
assert(false);
|
||||
}
|
||||
};
|
||||
|
||||
int main()
|
||||
{
|
||||
const int& iref = global_i;
|
||||
assert(&iref == &global_i);
|
||||
|
||||
TestingReferenceBinding ttt = global_i;
|
||||
ttt = global_i;
|
||||
|
||||
TestingReferenceBinding ttt2 = iref;
|
||||
ttt2 = iref;
|
||||
}
|
||||
|
||||
[endsect]
|
||||
|
||||
[endsect]
|
||||
@ -1,14 +0,0 @@
|
||||
index.html
|
||||
boost_optional/development.html
|
||||
boost_optional/synopsis.html
|
||||
boost_optional/detailed_semantics.html
|
||||
boost_optional/examples.html
|
||||
boost_optional/optional_references.html
|
||||
boost_optional/rebinding_semantics_for_assignment_of_optional_references.html
|
||||
boost_optional/in_place_factories.html
|
||||
boost_optional/a_note_about_optional_bool_.html
|
||||
boost_optional/exception_safety_guarantees.html
|
||||
boost_optional/type_requirements.html
|
||||
boost_optional/implementation_notes.html
|
||||
boost_optional/dependencies_and_portability.html
|
||||
boost_optional/acknowledgments.html
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>A note about optional<bool></title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="in_place_factories.html" title="In-Place Factories">
|
||||
@ -32,7 +32,7 @@
|
||||
be used with special caution and consideration.
|
||||
</p>
|
||||
<p>
|
||||
First, it is functionally similar to a tristate boolean (false,maybe,true)
|
||||
First, it is functionally similar to a tristate boolean (false, maybe, true)
|
||||
—such as <a href="../../../../../doc/html/tribool.html" target="_top">boost::tribool</a>—
|
||||
except that in a tristate boolean, the maybe state <span class="underline">represents
|
||||
a valid value</span>, unlike the corresponding state of an uninitialized
|
||||
@ -42,10 +42,11 @@
|
||||
needed.
|
||||
</p>
|
||||
<p>
|
||||
Second, <code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code>
|
||||
provides an implicit conversion to <code class="computeroutput"><span class="keyword">bool</span></code>.
|
||||
This conversion refers to the initialization state and not to the contained
|
||||
value. Using <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">bool</span><span class="special">></span></code> can
|
||||
Second, although <code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code>
|
||||
provides a contextual conversion to <code class="computeroutput"><span class="keyword">bool</span></code>
|
||||
in C++11, this falls back to an implicit conversion on older compilers. This
|
||||
conversion refers to the initialization state and not to the contained value.
|
||||
Using <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">bool</span><span class="special">></span></code> can
|
||||
lead to subtle errors due to the implicit <code class="computeroutput"><span class="keyword">bool</span></code>
|
||||
conversion:
|
||||
</p>
|
||||
@ -67,10 +68,33 @@
|
||||
takes an <code class="computeroutput"><span class="keyword">int</span></code> instead, it won't
|
||||
compile).
|
||||
</p>
|
||||
<p>
|
||||
Third, mixed comparisons with <code class="computeroutput"><span class="keyword">bool</span></code>
|
||||
work differently than similar mixed comparisons between pointers and <code class="computeroutput"><span class="keyword">bool</span></code>, so the results might surprise you:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">bool</span><span class="special">></span> <span class="identifier">oEmpty</span><span class="special">(</span><span class="identifier">none</span><span class="special">),</span> <span class="identifier">oTrue</span><span class="special">(</span><span class="keyword">true</span><span class="special">),</span> <span class="identifier">oFalse</span><span class="special">(</span><span class="keyword">false</span><span class="special">);</span>
|
||||
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span> <span class="comment">// renders true</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span> <span class="comment">// renders false!</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span> <span class="comment">// renders false!</span>
|
||||
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span> <span class="comment">// renders false</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span> <span class="comment">// renders true!</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span> <span class="comment">// renders false</span>
|
||||
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span> <span class="comment">// renders false</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span> <span class="comment">// renders false</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span> <span class="comment">// renders true</span>
|
||||
</pre>
|
||||
<p>
|
||||
In other words, for <code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code>, the following assertion does not hold:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">assert</span><span class="special">((</span><span class="identifier">opt</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">)</span> <span class="special">==</span> <span class="special">(!</span><span class="identifier">opt</span><span class="special">));</span>
|
||||
</pre>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Acknowledgments</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="dependencies_and_portability.html" title="Dependencies and Portability">
|
||||
@ -111,7 +111,7 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,11 +2,11 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Dependencies and Portability</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="implementation_notes.html" title="Implementation Notes">
|
||||
<link rel="prev" href="type_requirements.html" title="Type requirements">
|
||||
<link rel="next" href="acknowledgments.html" title="Acknowledgments">
|
||||
</head>
|
||||
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
||||
@ -20,21 +20,85 @@
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="implementation_notes.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgments.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
<a accesskey="p" href="type_requirements.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgments.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.dependencies_and_portability"></a><a class="link" href="dependencies_and_portability.html" title="Dependencies and Portability">Dependencies
|
||||
and Portability</a>
|
||||
</h2></div></div></div>
|
||||
<div class="toc"><dl class="toc"><dt><span class="section"><a href="dependencies_and_portability.html#boost_optional.dependencies_and_portability.optional_reference_binding">Optional
|
||||
Reference Binding</a></span></dt></dl></div>
|
||||
<p>
|
||||
The implementation uses <code class="computeroutput"><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">alignment_of</span><span class="special">.</span><span class="identifier">hpp</span></code> and
|
||||
<code class="computeroutput"><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">type_with_alignment</span><span class="special">.</span><span class="identifier">hpp</span></code>
|
||||
</p>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_optional.dependencies_and_portability.optional_reference_binding"></a><a class="link" href="dependencies_and_portability.html#boost_optional.dependencies_and_portability.optional_reference_binding" title="Optional Reference Binding">Optional
|
||||
Reference Binding</a>
|
||||
</h3></div></div></div>
|
||||
<p>
|
||||
On compilers that do not conform to Standard C++ rules of reference binding,
|
||||
operations on optional references might give adverse results: rather than
|
||||
binding a reference to a designated object they may create an unexpected
|
||||
temporary and bind to it. Compilers known to have these deficiencies include
|
||||
GCC versions 4.2, 4.3, 4.4, 4.5; QCC 4.4.2; MSVC versions 8.0, 9.0, 10.0,
|
||||
11.0, 12.0. On these compilers prefer using direct-initialization and copy
|
||||
assignment of optional references to copy-initialization and assignment from
|
||||
<code class="computeroutput"><span class="identifier">T</span><span class="special">&</span></code>:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&></span> <span class="identifier">or1</span><span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&></span> <span class="identifier">or2</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span> <span class="comment">// not portable</span>
|
||||
<span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span> <span class="comment">// not portable</span>
|
||||
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&></span> <span class="identifier">or3</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span> <span class="comment">// portable</span>
|
||||
<span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&>(</span><span class="identifier">i</span><span class="special">);</span> <span class="comment">// portable</span>
|
||||
</pre>
|
||||
<p>
|
||||
In order to check if your compiler correctly implements reference binding
|
||||
use this test program.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span>
|
||||
|
||||
<span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">global_i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
|
||||
|
||||
<span class="keyword">struct</span> <span class="identifier">TestingReferenceBinding</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">TestingReferenceBinding</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&</span> <span class="identifier">ii</span><span class="special">)</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">assert</span><span class="special">(&</span><span class="identifier">ii</span> <span class="special">==</span> <span class="special">&</span><span class="identifier">global_i</span><span class="special">);</span>
|
||||
<span class="special">}</span>
|
||||
|
||||
<span class="keyword">void</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&</span> <span class="identifier">ii</span><span class="special">)</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">assert</span><span class="special">(&</span><span class="identifier">ii</span> <span class="special">==</span> <span class="special">&</span><span class="identifier">global_i</span><span class="special">);</span>
|
||||
<span class="special">}</span>
|
||||
|
||||
<span class="keyword">void</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">int</span><span class="special">&&)</span> <span class="comment">// remove this if your compiler doesn't have rvalue refs</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="keyword">false</span><span class="special">);</span>
|
||||
<span class="special">}</span>
|
||||
<span class="special">};</span>
|
||||
|
||||
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">const</span> <span class="keyword">int</span><span class="special">&</span> <span class="identifier">iref</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
|
||||
<span class="identifier">assert</span><span class="special">(&</span><span class="identifier">iref</span> <span class="special">==</span> <span class="special">&</span><span class="identifier">global_i</span><span class="special">);</span>
|
||||
|
||||
<span class="identifier">TestingReferenceBinding</span> <span class="identifier">ttt</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
|
||||
<span class="identifier">ttt</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
|
||||
|
||||
<span class="identifier">TestingReferenceBinding</span> <span class="identifier">ttt2</span> <span class="special">=</span> <span class="identifier">iref</span><span class="special">;</span>
|
||||
<span class="identifier">ttt2</span> <span class="special">=</span> <span class="identifier">iref</span><span class="special">;</span>
|
||||
<span class="special">}</span>
|
||||
</pre>
|
||||
</div>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
@ -42,7 +106,7 @@
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="implementation_notes.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgments.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
<a accesskey="p" href="type_requirements.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgments.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Detailed Semantics</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="synopsis.html" title="Synopsis">
|
||||
@ -72,7 +72,7 @@
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_constructor"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">();</span></code>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
@ -82,11 +82,7 @@
|
||||
<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
Notes: T's default constructor <span class="underline">is not</span>
|
||||
called.
|
||||
<span class="bold"><strong>Notes:</strong></span> T's default constructor <span class="underline">is not</span> called.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
@ -99,7 +95,7 @@
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_constructor_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">none_t</span> <span class="special">);</span></code>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
@ -109,9 +105,6 @@
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
default constructor <span class="underline">is not</span> called.
|
||||
@ -132,12 +125,16 @@
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
|
||||
is <code class="computeroutput"><span class="keyword">true</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
|
||||
and its value is a<span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">v</span></code>.
|
||||
and its value is a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">v</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
||||
@ -193,6 +190,58 @@
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_constructor_move_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="identifier">v</span> <span class="special">)</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
|
||||
is <code class="computeroutput"><span class="keyword">true</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Directly-Move-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
|
||||
and its value is move-constructed from <code class="computeroutput"><span class="identifier">v</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
||||
<span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code> throws.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
||||
<span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code> is called.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
||||
be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
|
||||
in that case, the state of <code class="computeroutput"><span class="identifier">v</span></code>
|
||||
is determined by exception safety guarantees for <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v1</span><span class="special">,</span> <span class="identifier">v2</span><span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v1</span><span class="special">));</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v2</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">ref</span> <span class="special">)</span> <span class="special">=</span> <span class="keyword">delete</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> This constructor is deleted
|
||||
</li></ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
@ -229,6 +278,10 @@
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">);</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
|
||||
is <code class="computeroutput"><span class="keyword">true</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
||||
</li>
|
||||
@ -320,6 +373,116 @@
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_move_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
|
||||
<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
|
||||
is <code class="computeroutput"><span class="keyword">true</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initialized and its value is move constructed from <code class="computeroutput"><span class="identifier">rhs</span></code>;
|
||||
else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is uninitialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
||||
<span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code> throws.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span>
|
||||
<span class="special">&&</span> <span class="special">)</span></code>
|
||||
is called. The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code>
|
||||
is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
||||
be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
|
||||
in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
|
||||
initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
|
||||
of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uninit</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
|
||||
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
|
||||
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">uniqye_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">);</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">);</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="keyword">nullptr</span> <span class="special">);</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">);</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span> <span class="special">&&</span>
|
||||
<span class="identifier">rhs</span> <span class="special">);</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Move-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initialized and its value is another reference to the same object referenced
|
||||
by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
|
||||
else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is uninitialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
|
||||
will reefer to the same object (they alias).
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uninit</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
|
||||
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
|
||||
|
||||
<span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">v</span><span class="special">(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
||||
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
||||
|
||||
<span class="special">*</span><span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
|
||||
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
@ -368,6 +531,52 @@
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_move_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
|
||||
<span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span>
|
||||
<span class="identifier">rhs</span> <span class="special">);</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initialized and its value is move constructed from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
||||
<span class="identifier">U</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code> throws.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
||||
<span class="identifier">U</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code> is called if <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, which requires a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
|
||||
to <code class="computeroutput"><span class="identifier">T</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
|
||||
be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">);</span></code>
|
||||
in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
|
||||
initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
|
||||
guarantee of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
|
||||
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">x</span><span class="special">))</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
@ -420,6 +629,22 @@
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_operator_equal_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized destroys its contained
|
||||
value.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
@ -511,6 +736,66 @@
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_operator_move_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span>
|
||||
<span class="special">)</span> <span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Moves the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is moved
|
||||
from <code class="computeroutput"><span class="identifier">rhs</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
|
||||
or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span>
|
||||
<span class="special">&&)</span></code> throws.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
move-assignment operator is used, otherwise, its move-constructor is used.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
||||
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
||||
as far as <code class="computeroutput"><span class="identifier">optional</span></code> is concerned
|
||||
(it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
||||
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
|
||||
|
||||
<span class="identifier">T</span> <span class="identifier">y1</span><span class="special">,</span> <span class="identifier">y2</span><span class="special">,</span> <span class="identifier">yR</span><span class="special">;</span>
|
||||
<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y1</span><span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y2</span><span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="identifier">rhs</span> <span class="special">)</span>
|
||||
<span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> This assignment operator is deleted.
|
||||
</li></ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
@ -613,6 +898,75 @@
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_operator_move_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
|
||||
<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Move-assigns another <code class="computeroutput"><span class="identifier">optional</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initialized and its value is moved from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>, <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
remains initialized; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
||||
<span class="identifier">T</span> <span class="special">&&</span>
|
||||
<span class="special">)</span></code> throws.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
are initially initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<span class="emphasis"><em>move assignment operator</em></span> is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is
|
||||
initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s [destructor]
|
||||
is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initially uninitialized but <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s <span class="emphasis"><em>move
|
||||
constructor</em></span> is called. The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code>
|
||||
is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span>
|
||||
<span class="special">&&</span> <span class="identifier">is_nothrow_move_assignable</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
||||
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
||||
as far as optional is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
||||
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
||||
|
||||
<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&&</span>
|
||||
<span class="identifier">rhs</span> <span class="special">)</span>
|
||||
<span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Same as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span></code>.
|
||||
</li></ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
@ -673,6 +1027,59 @@
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_operator_move_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span>
|
||||
<span class="identifier">rhs</span> <span class="special">)</span>
|
||||
<span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Effect:</strong></span> Move-assigns another convertible
|
||||
optional to an optional.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initialized and its value is moved from the value of <code class="computeroutput"><span class="identifier">rhs</span></code>;
|
||||
else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is uninitialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
|
||||
or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
|
||||
throws.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
|
||||
are initially initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<span class="emphasis"><em>assignment operator</em></span> (from <code class="computeroutput"><span class="identifier">U</span><span class="special">&&</span></code>) is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<span class="emphasis"><em>destructor</em></span> is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially uninitialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<span class="emphasis"><em>converting constructor</em></span> (from <code class="computeroutput"><span class="identifier">U</span><span class="special">&&</span></code>) is called.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an exception,
|
||||
the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
|
||||
as far as optional is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
|
||||
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
|
||||
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
converting constructor fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
|
||||
|
||||
<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
@ -731,7 +1138,7 @@
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_reset"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="special">;</span></code>
|
||||
<code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
||||
<span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">detail</span><span class="special">::</span><span class="identifier">none_t</span> <span class="special">);</span></code>
|
||||
@ -768,7 +1175,7 @@
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requirements:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
|
||||
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns:</strong></span> A reference to the contained
|
||||
@ -870,7 +1277,7 @@
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requirements: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
|
||||
<span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span>
|
||||
@ -956,7 +1363,7 @@
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requirements: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized.
|
||||
<span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns:</strong></span> A pointer to the contained value.
|
||||
@ -981,16 +1388,19 @@
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span> </code><span class="emphasis"><em>unspecified-bool-type</em></span><code class="computeroutput"><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
|
||||
<code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns:</strong></span> An unspecified value which if
|
||||
used on a boolean context is equivalent to (<code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>)
|
||||
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> On compilers that do not support
|
||||
explicit conversion operators this falls back to safe-bool idiom.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
||||
@ -1005,16 +1415,13 @@
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_optional_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">!()</span> <span class="special">;</span></code>
|
||||
<code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">noexcept</span> <span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>;
|
||||
else <code class="computeroutput"><span class="keyword">false</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> This operator is provided for those
|
||||
compilers which can't use the <span class="emphasis"><em>unspecified-bool-type operator</em></span>
|
||||
@ -1039,9 +1446,9 @@
|
||||
<span class="keyword">const</span> <span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
||||
<span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">operator</span>
|
||||
</code><span class="emphasis"><em>unspecified-bool-type</em></span><code class="computeroutput"><span class="special">()</span>
|
||||
<span class="special">;</span></code>
|
||||
<span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">explicit</span>
|
||||
<span class="keyword">operator</span> <span class="keyword">bool</span>
|
||||
<span class="special">()</span> <span class="special">;</span></code>
|
||||
</li></ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
@ -1106,6 +1513,10 @@
|
||||
<span class="identifier">y</span> <span class="special">);</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
shall meet requirements of <code class="computeroutput"><span class="identifier">EqualityComparable</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code>
|
||||
and <code class="computeroutput"><span class="identifier">y</span></code> are initialized,
|
||||
@ -1162,6 +1573,10 @@
|
||||
<span class="identifier">y</span> <span class="special">);</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
shall meet requirements of <code class="computeroutput"><span class="identifier">LessThanComparable</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="identifier">y</span></code>
|
||||
is not initialized, <code class="computeroutput"><span class="keyword">false</span></code>.
|
||||
@ -1257,7 +1672,8 @@
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
|
||||
<span class="identifier">y</span><span class="special"><</span><span class="identifier">x</span> <span class="special">);</span></code>
|
||||
<span class="identifier">y</span> <span class="special"><</span>
|
||||
<span class="identifier">x</span> <span class="special">);</span></code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
@ -1282,13 +1698,40 @@
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
</ul></div>
|
||||
<a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
||||
<span class="special">==</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span>
|
||||
<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
need not meet requirements of <code class="computeroutput"><span class="identifier">EqualityComparable</span></code>.
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
|
||||
<span class="special">!=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span>
|
||||
<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
|
||||
<span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
|
||||
<span class="identifier">x</span> <span class="special">==</span>
|
||||
<span class="identifier">y</span> <span class="special">);</span></code>
|
||||
</li></ul></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
|
||||
<code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
|
||||
<span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span>
|
||||
<span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">y</span> <span class="special">);</span></code>
|
||||
<span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span></code>
|
||||
</p></blockquote></div>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
@ -1305,19 +1748,21 @@
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever
|
||||
<code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>
|
||||
throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code> throws.
|
||||
throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code> throws.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Notes:</strong></span> If both are initialized, <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>
|
||||
is used unqualified but with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">swap</span></code>
|
||||
introduced in scope. If only one is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span>
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
|
||||
is called.
|
||||
<span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code> is called.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Exception Safety:</strong></span> If both are initialized,
|
||||
this operation has the exception safety guarantees of <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>.
|
||||
If only one is initialized, it has the same basic guarantee as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>.
|
||||
If only one is initialized, it has the same basic guarantee as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span>
|
||||
<span class="special">)</span></code>.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<span class="bold"><strong>Example:</strong></span>
|
||||
@ -1345,7 +1790,7 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,11 +2,11 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Development</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="motivation.html" title="Motivation">
|
||||
<link rel="next" href="synopsis.html" title="Synopsis">
|
||||
</head>
|
||||
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
||||
@ -20,13 +20,13 @@
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="../index.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="synopsis.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
<a accesskey="p" href="motivation.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="synopsis.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.development"></a><a class="link" href="development.html" title="Development">Development</a>
|
||||
</h2></div></div></div>
|
||||
<div class="toc"><dl>
|
||||
<div class="toc"><dl class="toc">
|
||||
<dt><span class="section"><a href="development.html#boost_optional.development.the_models">The models</a></span></dt>
|
||||
<dt><span class="section"><a href="development.html#boost_optional.development.the_semantics">The semantics</a></span></dt>
|
||||
<dt><span class="section"><a href="development.html#boost_optional.development.the_interface">The Interface</a></span></dt>
|
||||
@ -399,7 +399,7 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
@ -407,7 +407,7 @@
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="../index.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="synopsis.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
<a accesskey="p" href="motivation.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="synopsis.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Examples</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="detailed_semantics.html" title="Detailed Semantics">
|
||||
@ -26,7 +26,7 @@
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.examples"></a><a class="link" href="examples.html" title="Examples">Examples</a>
|
||||
</h2></div></div></div>
|
||||
<div class="toc"><dl>
|
||||
<div class="toc"><dl class="toc">
|
||||
<dt><span class="section"><a href="examples.html#boost_optional.examples.optional_return_values">Optional
|
||||
return values</a></span></dt>
|
||||
<dt><span class="section"><a href="examples.html#boost_optional.examples.optional_local_variables">Optional
|
||||
@ -133,7 +133,7 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Exception Safety Guarantees</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="a_note_about_optional_bool_.html" title="A note about optional<bool>">
|
||||
@ -28,8 +28,36 @@
|
||||
Guarantees</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
Because of the current implementation (see <a class="link" href="implementation_notes.html" title="Implementation Notes">Implementation
|
||||
Notes</a>), all of the assignment methods:
|
||||
This library assumes that <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
destructor does not throw exceptions. If it does, the behaviour of many operations
|
||||
on <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is
|
||||
undefined.
|
||||
</p>
|
||||
<p>
|
||||
The following mutating operations never throw exceptions:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span></code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span></code>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
In addition, the following constructors and the destructor never throw exceptions:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span>
|
||||
<span class="keyword">noexcept</span></code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span></code>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
Regarding the following assignment functions:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
@ -52,93 +80,76 @@
|
||||
<span class="special">)</span> </code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&)</span></code>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
Can only <span class="emphasis"><em>guarantee</em></span> the <span class="underline">basic
|
||||
exception safety</span>: The lvalue optional is left <span class="underline">uninitialized</span>
|
||||
if an exception is thrown (any previous value is <span class="emphasis"><em>first</em></span>
|
||||
destroyed using <code class="computeroutput"><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>)
|
||||
They forward calls to the corresponding <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
constructors or assignments (depending on whether the optional object is initialized
|
||||
or not); so if both <code class="computeroutput"><span class="identifier">T</span></code>'s constructor
|
||||
and the assignment provide strong exception safety guarantee, <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>'s assignment
|
||||
also provides strong exception safety guarantee; otherwise we only get the
|
||||
basic guarantee. Additionally, if both involved <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
constructor and the assignment never throw, <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>'s
|
||||
assignment also never throws.
|
||||
</p>
|
||||
<p>
|
||||
On the other hand, the <span class="emphasis"><em>uninitializing</em></span> methods:
|
||||
Unless <code class="computeroutput"><span class="identifier">T</span></code>'s constructor or assignment
|
||||
throws, <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> does
|
||||
not throw anything else on its own. A throw during assignment never changes
|
||||
the initialization state of any optional object involved:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">detail</span><span class="special">::</span><span class="identifier">none_t</span> <span class="special">)</span></code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span></code>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
Provide the no-throw guarantee (assuming a no-throw <code class="computeroutput"><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>)
|
||||
</p>
|
||||
<p>
|
||||
However, since <code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code>
|
||||
itself doesn't throw any exceptions, the only source for exceptions here are
|
||||
<code class="computeroutput"><span class="identifier">T</span></code>'s constructor, so if you
|
||||
know the exception guarantees for <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span>
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>, you
|
||||
know that <code class="computeroutput"><span class="identifier">optional</span></code>'s assignment
|
||||
and reset has the same guarantees.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="comment">//</span>
|
||||
<span class="comment">// Case 1: Exception thrown during assignment.</span>
|
||||
<span class="comment">//</span>
|
||||
<span class="identifier">T</span> <span class="identifier">v0</span><span class="special">(</span><span class="number">123</span><span class="special">);</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v0</span><span class="special">);</span>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">(</span><span class="identifier">val1</span><span class="special">);</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt2</span><span class="special">(</span><span class="identifier">val2</span><span class="special">);</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">opt1</span><span class="special">);</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">opt2</span><span class="special">);</span>
|
||||
|
||||
<span class="keyword">try</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">T</span> <span class="identifier">v1</span><span class="special">(</span><span class="number">456</span><span class="special">);</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">(</span><span class="identifier">v1</span><span class="special">);</span>
|
||||
<span class="identifier">opt0</span> <span class="special">=</span> <span class="identifier">opt1</span> <span class="special">;</span>
|
||||
|
||||
<span class="comment">// If no exception was thrown, assignment succeeded.</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">opt0</span> <span class="special">==</span> <span class="identifier">v1</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">opt2</span><span class="special">;</span> <span class="comment">// throws</span>
|
||||
<span class="special">}</span>
|
||||
<span class="keyword">catch</span><span class="special">(...)</span>
|
||||
<span class="special">{</span>
|
||||
<span class="comment">// If any exception was thrown, 'opt0' is reset to uninitialized.</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span> <span class="special">!</span><span class="identifier">opt0</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="special">}</span>
|
||||
|
||||
<span class="comment">//</span>
|
||||
<span class="comment">// Case 2: Exception thrown during reset(v)</span>
|
||||
<span class="comment">//</span>
|
||||
<span class="identifier">T</span> <span class="identifier">v0</span><span class="special">(</span><span class="number">123</span><span class="special">);</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v0</span><span class="special">);</span>
|
||||
<span class="keyword">try</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">T</span> <span class="identifier">v1</span><span class="special">(</span><span class="number">456</span><span class="special">);</span>
|
||||
<span class="identifier">opt</span><span class="special">.</span><span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">v1</span> <span class="special">)</span> <span class="special">;</span>
|
||||
|
||||
<span class="comment">// If no exception was thrown, reset succeeded.</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v1</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="special">}</span>
|
||||
<span class="keyword">catch</span><span class="special">(...)</span>
|
||||
<span class="special">{</span>
|
||||
<span class="comment">// If any exception was thrown, 'opt' is reset to uninitialized.</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span> <span class="special">!</span><span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">opt1</span><span class="special">);</span>
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">opt2</span><span class="special">);</span>
|
||||
<span class="special">}</span>
|
||||
</pre>
|
||||
<p>
|
||||
This also applies to move assignments/constructors. However, move operations
|
||||
are made no-throw more often.
|
||||
</p>
|
||||
<h4>
|
||||
<a name="boost_optional.exception_safety_guarantees.h0"></a>
|
||||
<span class="phrase"><a name="boost_optional.exception_safety_guarantees.swap"></a></span><a class="link" href="exception_safety_guarantees.html#boost_optional.exception_safety_guarantees.swap">Swap</a>
|
||||
</h4>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span><span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&,</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="special">)</span></code> has the same exception guarantee as <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>
|
||||
when both optionals are initialized. If only one of the optionals is initialized,
|
||||
it gives the same <span class="emphasis"><em>basic</em></span> exception guarantee as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code> (since
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span></code> doesn't throw). If none of the optionals
|
||||
is initialized, it has no-throw guarantee since it is a no-op.
|
||||
Unless <code class="computeroutput"><span class="identifier">swap</span></code> on optional is
|
||||
customized, its primary implementation forwards calls to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<code class="computeroutput"><span class="identifier">swap</span></code> or move constructor (depending
|
||||
on the initialization state of the optional objects). Thus, if both <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="identifier">swap</span></code>
|
||||
and move constructor never throw, <code class="computeroutput"><span class="identifier">swap</span></code>
|
||||
on <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> never
|
||||
throws. similarly, if both <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<code class="computeroutput"><span class="identifier">swap</span></code> and move constructor offer
|
||||
strong guarantee, <code class="computeroutput"><span class="identifier">swap</span></code> on
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> also
|
||||
offers a strong guarantee.
|
||||
</p>
|
||||
<p>
|
||||
In case <code class="computeroutput"><span class="identifier">swap</span></code> on optional is
|
||||
customized, the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
move constructor are replaced with the calls to <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
default constructor followed by <code class="computeroutput"><span class="identifier">swap</span></code>.
|
||||
(This is more useful on older compilers that do not support move semantics,
|
||||
when one wants to acheive stronger exception safety guarantees.) In this case
|
||||
the exception safety guarantees for <code class="computeroutput"><span class="identifier">swap</span></code>
|
||||
are reliant on the guarantees of <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
<code class="computeroutput"><span class="identifier">swap</span></code> and default constructor
|
||||
</p>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Implementation Notes</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="type_requirements.html" title="Type requirements">
|
||||
@ -31,17 +31,17 @@
|
||||
currently implemented using a custom aligned storage facility built from <code class="computeroutput"><span class="identifier">alignment_of</span></code> and <code class="computeroutput"><span class="identifier">type_with_alignment</span></code>
|
||||
(both from Type Traits). It uses a separate boolean flag to indicate the initialization
|
||||
state. Placement new with <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
copy constructor and <code class="computeroutput"><span class="identifier">T</span></code>'s destructor
|
||||
are explicitly used to initialize,copy and destroy optional values. As a result,
|
||||
<code class="computeroutput"><span class="identifier">T</span></code>'s default constructor is
|
||||
effectively by-passed, but the exception guarantees are basic. It is planned
|
||||
to replace the current implementation with another with stronger exception
|
||||
safety, such as a future <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">variant</span></code>.
|
||||
copy/move constructor and <code class="computeroutput"><span class="identifier">T</span></code>'s
|
||||
destructor are explicitly used to initialize, copy, move and destroy optional
|
||||
values. As a result, <code class="computeroutput"><span class="identifier">T</span></code>'s default
|
||||
constructor is effectively by-passed, but the exception guarantees are basic.
|
||||
It is planned to replace the current implementation with another with stronger
|
||||
exception safety, such as a future <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">variant</span></code>.
|
||||
</p>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>In-Place Factories</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">
|
||||
@ -182,7 +182,7 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
128
doc/html/boost_optional/motivation.html
Normal file
128
doc/html/boost_optional/motivation.html
Normal file
@ -0,0 +1,128 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Motivation</title>
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="next" href="development.html" title="Development">
|
||||
</head>
|
||||
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
||||
<table cellpadding="2" width="100%"><tr>
|
||||
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td>
|
||||
<td align="center"><a href="../../../../../index.html">Home</a></td>
|
||||
<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td>
|
||||
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
|
||||
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
|
||||
<td align="center"><a href="../../../../../more/index.htm">More</a></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="../index.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="development.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.motivation"></a><a class="link" href="motivation.html" title="Motivation">Motivation</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
Consider these functions which should return a value but which might not have
|
||||
a value to return:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
(A) <code class="computeroutput"><span class="keyword">double</span> <span class="identifier">sqrt</span><span class="special">(</span><span class="keyword">double</span> <span class="identifier">n</span> <span class="special">);</span></code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
(B) <code class="computeroutput"><span class="keyword">char</span> <span class="identifier">get_async_input</span><span class="special">();</span></code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
(C) <code class="computeroutput"><span class="identifier">point</span> <span class="identifier">polygon</span><span class="special">::</span><span class="identifier">get_any_point_effectively_inside</span><span class="special">();</span></code>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
There are different approaches to the issue of not having a value to return.
|
||||
</p>
|
||||
<p>
|
||||
A typical approach is to consider the existence of a valid return value as
|
||||
a postcondition, so that if the function cannot compute the value to return,
|
||||
it has either undefined behavior (and can use assert in a debug build) or uses
|
||||
a runtime check and throws an exception if the postcondition is violated. This
|
||||
is a reasonable choice for example, for function (A), because the lack of a
|
||||
proper return value is directly related to an invalid parameter (out of domain
|
||||
argument), so it is appropriate to require the callee to supply only parameters
|
||||
in a valid domain for execution to continue normally.
|
||||
</p>
|
||||
<p>
|
||||
However, function (B), because of its asynchronous nature, does not fail just
|
||||
because it can't find a value to return; so it is incorrect to consider such
|
||||
a situation an error and assert or throw an exception. This function must return,
|
||||
and somehow, must tell the callee that it is not returning a meaningful value.
|
||||
</p>
|
||||
<p>
|
||||
A similar situation occurs with function (C): it is conceptually an error to
|
||||
ask a <span class="emphasis"><em>null-area</em></span> polygon to return a point inside itself,
|
||||
but in many applications, it is just impractical for performance reasons to
|
||||
treat this as an error (because detecting that the polygon has no area might
|
||||
be too expensive to be required to be tested previously), and either an arbitrary
|
||||
point (typically at infinity) is returned, or some efficient way to tell the
|
||||
callee that there is no such point is used.
|
||||
</p>
|
||||
<p>
|
||||
There are various mechanisms to let functions communicate that the returned
|
||||
value is not valid. One such mechanism, which is quite common since it has
|
||||
zero or negligible overhead, is to use a special value which is reserved to
|
||||
communicate this. Classical examples of such special values are <code class="computeroutput"><span class="identifier">EOF</span></code>, <code class="computeroutput"><span class="identifier">string</span><span class="special">::</span><span class="identifier">npos</span></code>, points
|
||||
at infinity, etc...
|
||||
</p>
|
||||
<p>
|
||||
When those values exist, i.e. the return type can hold all meaningful values
|
||||
<span class="emphasis"><em>plus</em></span> the <span class="emphasis"><em>signal</em></span> value, this mechanism
|
||||
is quite appropriate and well known. Unfortunately, there are cases when such
|
||||
values do not exist. In these cases, the usual alternative is either to use
|
||||
a wider type, such as <code class="computeroutput"><span class="keyword">int</span></code> in place
|
||||
of <code class="computeroutput"><span class="keyword">char</span></code>; or a compound type, such
|
||||
as <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">point</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span></code>.
|
||||
</p>
|
||||
<p>
|
||||
Returning a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span></code>, thus attaching a boolean flag to the result
|
||||
which indicates if the result is meaningful, has the advantage that can be
|
||||
turned into a consistent idiom since the first element of the pair can be whatever
|
||||
the function would conceptually return. For example, the last two functions
|
||||
could have the following interface:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="keyword">char</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span> <span class="identifier">get_async_input</span><span class="special">();</span>
|
||||
<span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">point</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span> <span class="identifier">polygon</span><span class="special">::</span><span class="identifier">get_any_point_effectively_inside</span><span class="special">();</span>
|
||||
</pre>
|
||||
<p>
|
||||
These functions use a consistent interface for dealing with possibly nonexistent
|
||||
results:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">point</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">poly</span><span class="special">.</span><span class="identifier">get_any_point_effectively_inside</span><span class="special">();</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span> <span class="identifier">p</span><span class="special">.</span><span class="identifier">second</span> <span class="special">)</span>
|
||||
<span class="identifier">flood_fill</span><span class="special">(</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">first</span><span class="special">);</span>
|
||||
</pre>
|
||||
<p>
|
||||
However, not only is this quite a burden syntactically, it is also error prone
|
||||
since the user can easily use the function result (first element of the pair)
|
||||
without ever checking if it has a valid value.
|
||||
</p>
|
||||
<p>
|
||||
Clearly, we need a better idiom.
|
||||
</p>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
</div></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="../index.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="development.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Optional references</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="examples.html" title="Examples">
|
||||
@ -60,7 +60,7 @@
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
Copies of <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>
|
||||
will copy the references but all these references will nonetheless reefer
|
||||
will copy the references but all these references will nonetheless refer
|
||||
to the same object.
|
||||
</li>
|
||||
<li class="listitem">
|
||||
@ -68,10 +68,39 @@
|
||||
than the reference itself.
|
||||
</li>
|
||||
</ul></div>
|
||||
<div class="warning"><table border="0" summary="Warning">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../doc/src/images/warning.png"></td>
|
||||
<th align="left">Warning</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
On compilers that do not conform to Standard C++ rules of reference binding,
|
||||
operations on optional references might give adverse results: rather than
|
||||
binding a reference to a designated object they may create an unexpected
|
||||
temporary and bind to it. For more details see <a class="link" href="dependencies_and_portability.html#boost_optional.dependencies_and_portability.optional_reference_binding" title="Optional Reference Binding">Dependencies
|
||||
and Portability section</a>.
|
||||
</p></td></tr>
|
||||
</table></div>
|
||||
<h4>
|
||||
<a name="boost_optional.optional_references.h0"></a>
|
||||
<span class="phrase"><a name="boost_optional.optional_references.rvalue_references"></a></span><a class="link" href="optional_references.html#boost_optional.optional_references.rvalue_references">Rvalue
|
||||
references</a>
|
||||
</h4>
|
||||
<p>
|
||||
Rvalue references and lvalue references to const have the ability in C++ to
|
||||
extend the life time of a temporary they bind to. Optional references do not
|
||||
have this capability, therefore to avoid surprising effects it is not possible
|
||||
to initialize an optional references from a temporary. Optional rvalue references
|
||||
are disabled altogether. Also, the initialization and assignment of an optional
|
||||
reference to const from rvalue reference is disabled.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> <span class="comment">// legal</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&></span> <span class="identifier">oi</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> <span class="comment">// illegal</span>
|
||||
</pre>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Rebinding semantics for assignment of optional references</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="optional_references.html" title="Optional references">
|
||||
@ -134,7 +134,7 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,8 +2,8 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Synopsis</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="development.html" title="Development">
|
||||
@ -37,31 +37,43 @@
|
||||
|
||||
<span class="comment">// (If T is of reference type, the parameters and results by reference are by value)</span>
|
||||
|
||||
<span class="identifier">optional</span> <span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">optional</span> <span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_none_t"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_none_t"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_move_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="comment">// [new in 1.34]</span>
|
||||
<span class="identifier">optional</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_bool_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span><span class="emphasis"><em>see below</em></span><span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_move_constructor_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_other_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_move_constructor_other_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_equal_none_t"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_equal_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_move_equal_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_equal_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span><span class="emphasis"><em>see below</em></span><span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_move_equal_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_equal_other_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_move_equal_other_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
@ -81,14 +93,14 @@
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">operator</span> <span class="identifier">unspecified</span><span class="special">-</span><span class="keyword">bool</span><span class="special">-</span><span class="identifier">type</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_bool"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_bool"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_not"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_not"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="comment">// deprecated methods</span>
|
||||
|
||||
<span class="comment">// (deprecated)</span>
|
||||
<span class="keyword">void</span> <span class="identifier">reset</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_reset"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="keyword">void</span> <span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_reset"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="comment">// (deprecated)</span>
|
||||
<span class="keyword">void</span> <span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_reset_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
@ -110,6 +122,10 @@
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">>=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_operator_compare_greater_or_equal_optional_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">==</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_operator_compare_equal_optional_none"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">!=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_operator_compare_not_equal_optional_none"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="comment">// [new in 1.34]</span>
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">inline</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">make_optional</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_make_optional_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
@ -138,7 +154,7 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
@ -2,12 +2,12 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Type requirements</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="prev" href="exception_safety_guarantees.html" title="Exception Safety Guarantees">
|
||||
<link rel="next" href="implementation_notes.html" title="Implementation Notes">
|
||||
<link rel="next" href="dependencies_and_portability.html" title="Dependencies and Portability">
|
||||
</head>
|
||||
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
||||
<table cellpadding="2" width="100%"><tr>
|
||||
@ -20,16 +20,16 @@
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="exception_safety_guarantees.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="implementation_notes.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
<a accesskey="p" href="exception_safety_guarantees.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.type_requirements"></a><a class="link" href="type_requirements.html" title="Type requirements">Type requirements</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
In general, <code class="computeroutput"><span class="identifier">T</span></code> must be <a href="../../../../utility/CopyConstructible.html" target="_top">Copy Constructible</a> and
|
||||
have a no-throw destructor. The copy-constructible requirement is not needed
|
||||
if <span class="bold"><strong>InPlaceFactories</strong></span> are used.
|
||||
In general, <code class="computeroutput"><span class="identifier">T</span></code> must be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> and have a no-throw destructor.
|
||||
The <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> requirement
|
||||
is not needed if <span class="bold"><strong>InPlaceFactories</strong></span> are used.
|
||||
</p>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">T</span></code> <span class="underline">is
|
||||
@ -39,7 +39,7 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<p>
|
||||
<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014 Andrzej Krzemieński<p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
@ -47,7 +47,7 @@
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="exception_safety_guarantees.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="implementation_notes.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
<a accesskey="p" href="exception_safety_guarantees.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@ -1,582 +0,0 @@
|
||||
/*=============================================================================
|
||||
Copyright (c) 2004 Joel de Guzman
|
||||
http://spirit.sourceforge.net/
|
||||
|
||||
Use, modification and distribution is subject to the Boost Software
|
||||
License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
http://www.boost.org/LICENSE_1_0.txt)
|
||||
=============================================================================*/
|
||||
|
||||
/*=============================================================================
|
||||
Body defaults
|
||||
=============================================================================*/
|
||||
|
||||
body
|
||||
{
|
||||
margin: 1em;
|
||||
font-family: sans-serif;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Paragraphs
|
||||
=============================================================================*/
|
||||
|
||||
p
|
||||
{
|
||||
text-align: left;
|
||||
font-size: 10pt;
|
||||
line-height: 1.15;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Program listings
|
||||
=============================================================================*/
|
||||
|
||||
/* Code on paragraphs */
|
||||
p tt.computeroutput
|
||||
{
|
||||
font-size: 10pt;
|
||||
}
|
||||
|
||||
pre.synopsis
|
||||
{
|
||||
font-size: 10pt;
|
||||
margin: 1pc 4% 0pc 4%;
|
||||
padding: 0.5pc 0.5pc 0.5pc 0.5pc;
|
||||
}
|
||||
|
||||
.programlisting,
|
||||
.screen
|
||||
{
|
||||
font-size: 10pt;
|
||||
display: block;
|
||||
margin: 1pc 4% 0pc 4%;
|
||||
padding: 0.5pc 0.5pc 0.5pc 0.5pc;
|
||||
}
|
||||
|
||||
/* Program listings in tables don't get borders */
|
||||
td .programlisting,
|
||||
td .screen
|
||||
{
|
||||
margin: 0pc 0pc 0pc 0pc;
|
||||
padding: 0pc 0pc 0pc 0pc;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Headings
|
||||
=============================================================================*/
|
||||
|
||||
h1, h2, h3, h4, h5, h6
|
||||
{
|
||||
text-align: left;
|
||||
margin: 1em 0em 0.5em 0em;
|
||||
font-weight: bold;
|
||||
}
|
||||
|
||||
h1 { font: 140% }
|
||||
h2 { font: bold 140% }
|
||||
h3 { font: bold 130% }
|
||||
h4 { font: bold 120% }
|
||||
h5 { font: italic 110% }
|
||||
h6 { font: italic 100% }
|
||||
|
||||
/* Top page titles */
|
||||
title,
|
||||
h1.title,
|
||||
h2.title
|
||||
h3.title,
|
||||
h4.title,
|
||||
h5.title,
|
||||
h6.title,
|
||||
.refentrytitle
|
||||
{
|
||||
font-weight: bold;
|
||||
margin-bottom: 1pc;
|
||||
}
|
||||
|
||||
h1.title { font-size: 140% }
|
||||
h2.title { font-size: 140% }
|
||||
h3.title { font-size: 130% }
|
||||
h4.title { font-size: 120% }
|
||||
h5.title { font-size: 110% }
|
||||
h6.title { font-size: 100% }
|
||||
|
||||
.section h1
|
||||
{
|
||||
margin: 0em 0em 0.5em 0em;
|
||||
font-size: 140%;
|
||||
}
|
||||
|
||||
.section h2 { font-size: 140% }
|
||||
.section h3 { font-size: 130% }
|
||||
.section h4 { font-size: 120% }
|
||||
.section h5 { font-size: 110% }
|
||||
.section h6 { font-size: 100% }
|
||||
|
||||
/* Code on titles */
|
||||
h1 tt.computeroutput { font-size: 140% }
|
||||
h2 tt.computeroutput { font-size: 140% }
|
||||
h3 tt.computeroutput { font-size: 130% }
|
||||
h4 tt.computeroutput { font-size: 120% }
|
||||
h5 tt.computeroutput { font-size: 110% }
|
||||
h6 tt.computeroutput { font-size: 100% }
|
||||
|
||||
/*=============================================================================
|
||||
Author
|
||||
=============================================================================*/
|
||||
|
||||
h3.author
|
||||
{
|
||||
font-size: 100%
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Lists
|
||||
=============================================================================*/
|
||||
|
||||
li
|
||||
{
|
||||
font-size: 10pt;
|
||||
line-height: 1.3;
|
||||
}
|
||||
|
||||
/* Unordered lists */
|
||||
ul
|
||||
{
|
||||
text-align: left;
|
||||
}
|
||||
|
||||
/* Ordered lists */
|
||||
ol
|
||||
{
|
||||
text-align: left;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Links
|
||||
=============================================================================*/
|
||||
|
||||
a
|
||||
{
|
||||
text-decoration: none; /* no underline */
|
||||
}
|
||||
|
||||
a:hover
|
||||
{
|
||||
text-decoration: underline;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Spirit style navigation
|
||||
=============================================================================*/
|
||||
|
||||
.spirit-nav
|
||||
{
|
||||
text-align: right;
|
||||
}
|
||||
|
||||
.spirit-nav a
|
||||
{
|
||||
color: white;
|
||||
padding-left: 0.5em;
|
||||
}
|
||||
|
||||
.spirit-nav img
|
||||
{
|
||||
border-width: 0px;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Table of contents
|
||||
=============================================================================*/
|
||||
|
||||
.toc
|
||||
{
|
||||
margin: 1pc 4% 0pc 4%;
|
||||
padding: 0.1pc 1pc 0.1pc 1pc;
|
||||
font-size: 10pt;
|
||||
line-height: 1.15;
|
||||
}
|
||||
|
||||
.toc-main
|
||||
{
|
||||
text-align: center;
|
||||
margin: 3pc 16% 3pc 16%;
|
||||
padding: 3pc 1pc 3pc 1pc;
|
||||
line-height: 0.1;
|
||||
}
|
||||
|
||||
.boost-toc
|
||||
{
|
||||
float: right;
|
||||
padding: 0.5pc;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Tables
|
||||
=============================================================================*/
|
||||
|
||||
.table-title,
|
||||
div.table p.title
|
||||
{
|
||||
margin-left: 4%;
|
||||
padding-right: 0.5em;
|
||||
padding-left: 0.5em;
|
||||
}
|
||||
|
||||
.informaltable table,
|
||||
.table table
|
||||
{
|
||||
width: 92%;
|
||||
margin-left: 4%;
|
||||
margin-right: 4%;
|
||||
}
|
||||
|
||||
div.informaltable table,
|
||||
div.table table
|
||||
{
|
||||
padding: 4px;
|
||||
}
|
||||
|
||||
/* Table Cells */
|
||||
div.informaltable table tr td,
|
||||
div.table table tr td
|
||||
{
|
||||
padding: 0.5em;
|
||||
text-align: left;
|
||||
}
|
||||
|
||||
div.informaltable table tr th,
|
||||
div.table table tr th
|
||||
{
|
||||
padding: 0.5em 0.5em 0.5em 0.5em;
|
||||
border: 1pt solid white;
|
||||
font-size: 120%;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Blurbs
|
||||
=============================================================================*/
|
||||
|
||||
div.note,
|
||||
div.tip,
|
||||
div.important,
|
||||
div.caution,
|
||||
div.warning,
|
||||
div.sidebar
|
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{
|
||||
font-size: 10pt;
|
||||
line-height: 1.2;
|
||||
display: block;
|
||||
margin: 1pc 4% 0pc 4%;
|
||||
padding: 0.5pc 0.5pc 0.5pc 0.5pc;
|
||||
}
|
||||
|
||||
div.sidebar img
|
||||
{
|
||||
padding: 1pt;
|
||||
}
|
||||
|
||||
|
||||
|
||||
/*=============================================================================
|
||||
Callouts
|
||||
=============================================================================*/
|
||||
.line_callout_bug img
|
||||
{
|
||||
float: left;
|
||||
position:relative;
|
||||
left: 4px;
|
||||
top: -12px;
|
||||
clear: left;
|
||||
margin-left:-22px;
|
||||
}
|
||||
|
||||
.callout_bug img
|
||||
{
|
||||
}
|
||||
|
||||
|
||||
|
||||
/*=============================================================================
|
||||
Variable Lists
|
||||
=============================================================================*/
|
||||
|
||||
/* Make the terms in definition lists bold */
|
||||
div.variablelist dl dt,
|
||||
span.term
|
||||
{
|
||||
font-weight: bold;
|
||||
font-size: 10pt;
|
||||
}
|
||||
|
||||
div.variablelist table tbody tr td
|
||||
{
|
||||
text-align: left;
|
||||
vertical-align: top;
|
||||
padding: 0em 2em 0em 0em;
|
||||
font-size: 10pt;
|
||||
margin: 0em 0em 0.5em 0em;
|
||||
line-height: 1;
|
||||
}
|
||||
|
||||
/* Make the terms in definition lists bold */
|
||||
div.variablelist dl dt
|
||||
{
|
||||
margin-bottom: 0.2em;
|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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div.note,
|
||||
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|
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|
||||
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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||||
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|
||||
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|
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||||
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|
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|
||||
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|
||||
|
||||
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|
||||
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||||
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|
||||
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|
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|
||||
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|
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|
||||
/* Tables */
|
||||
div.informaltable table tr td,
|
||||
div.table table tr td
|
||||
{
|
||||
border: 1px solid #DCDCDC;
|
||||
background-color: #FAFFFB;
|
||||
}
|
||||
|
||||
div.informaltable table tr th,
|
||||
div.table table tr th
|
||||
{
|
||||
border: 1px solid #DCDCDC;
|
||||
background-color: #FAFFFB;
|
||||
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|
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|
||||
/* Misc */
|
||||
span.highlight
|
||||
{
|
||||
font-weight: bold;
|
||||
}
|
||||
}
|
||||
@ -2,10 +2,10 @@
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
||||
<title>Chapter 1. Boost.Optional</title>
|
||||
<link rel="stylesheet" href="boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
|
||||
<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
||||
<link rel="home" href="index.html" title="Chapter 1. Boost.Optional">
|
||||
<link rel="next" href="boost_optional/development.html" title="Development">
|
||||
<link rel="next" href="boost_optional/motivation.html" title="Motivation">
|
||||
</head>
|
||||
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
||||
<table cellpadding="2" width="100%"><tr>
|
||||
@ -17,7 +17,7 @@
|
||||
<td align="center"><a href="../../../../more/index.htm">More</a></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav"><a accesskey="n" href="boost_optional/development.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a></div>
|
||||
<div class="spirit-nav"><a accesskey="n" href="boost_optional/motivation.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a></div>
|
||||
<div class="chapter">
|
||||
<div class="titlepage"><div>
|
||||
<div><h2 class="title">
|
||||
@ -26,6 +26,7 @@
|
||||
<span class="firstname">Fernando Luis</span> <span class="surname">Cacciola Carballal</span>
|
||||
</h3></div></div>
|
||||
<div><p class="copyright">Copyright © 2003-2007 Fernando Luis Cacciola Carballal</p></div>
|
||||
<div><p class="copyright">Copyright © 2014 Andrzej Krzemieński</p></div>
|
||||
<div><div class="legalnotice">
|
||||
<a name="optional.legal"></a><p>
|
||||
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
@ -35,8 +36,9 @@
|
||||
</div></div>
|
||||
<div class="toc">
|
||||
<p><b>Table of Contents</b></p>
|
||||
<dl>
|
||||
<dt><span class="section"><a href="index.html#optional.motivation">Motivation</a></span></dt>
|
||||
<dl class="toc">
|
||||
<dt><span class="section"><a href="index.html#optional.introduction">Introduction</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/motivation.html">Motivation</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/development.html">Development</a></span></dt>
|
||||
<dd><dl>
|
||||
<dt><span class="section"><a href="boost_optional/development.html#boost_optional.development.the_models">The models</a></span></dt>
|
||||
@ -65,108 +67,35 @@
|
||||
<dt><span class="section"><a href="boost_optional/exception_safety_guarantees.html">Exception Safety
|
||||
Guarantees</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/type_requirements.html">Type requirements</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/implementation_notes.html">Implementation Notes</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/dependencies_and_portability.html">Dependencies
|
||||
and Portability</a></span></dt>
|
||||
<dd><dl><dt><span class="section"><a href="boost_optional/dependencies_and_portability.html#boost_optional.dependencies_and_portability.optional_reference_binding">Optional
|
||||
Reference Binding</a></span></dt></dl></dd>
|
||||
<dt><span class="section"><a href="boost_optional/acknowledgments.html">Acknowledgments</a></span></dt>
|
||||
</dl>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="optional.motivation"></a><a class="link" href="index.html#optional.motivation" title="Motivation">Motivation</a>
|
||||
<a name="optional.introduction"></a><a class="link" href="index.html#optional.introduction" title="Introduction">Introduction</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
Consider these functions which should return a value but which might not have
|
||||
a value to return:
|
||||
This library can be used to represent 'optional' (or 'nullable') objects that
|
||||
can be safely passed by value:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||||
<li class="listitem">
|
||||
(A) <code class="computeroutput"><span class="keyword">double</span> <span class="identifier">sqrt</span><span class="special">(</span><span class="keyword">double</span> <span class="identifier">n</span> <span class="special">);</span></code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
(B) <code class="computeroutput"><span class="keyword">char</span> <span class="identifier">get_async_input</span><span class="special">();</span></code>
|
||||
</li>
|
||||
<li class="listitem">
|
||||
(C) <code class="computeroutput"><span class="identifier">point</span> <span class="identifier">polygon</span><span class="special">::</span><span class="identifier">get_any_point_effectively_inside</span><span class="special">();</span></code>
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
There are different approaches to the issue of not having a value to return.
|
||||
</p>
|
||||
<p>
|
||||
A typical approach is to consider the existence of a valid return value as
|
||||
a postcondition, so that if the function cannot compute the value to return,
|
||||
it has either undefined behavior (and can use assert in a debug build) or uses
|
||||
a runtime check and throws an exception if the postcondition is violated. This
|
||||
is a reasonable choice for example, for function (A), because the lack of a
|
||||
proper return value is directly related to an invalid parameter (out of domain
|
||||
argument), so it is appropriate to require the callee to supply only parameters
|
||||
in a valid domain for execution to continue normally.
|
||||
</p>
|
||||
<p>
|
||||
However, function (B), because of its asynchronous nature, does not fail just
|
||||
because it can't find a value to return; so it is incorrect to consider such
|
||||
a situation an error and assert or throw an exception. This function must return,
|
||||
and somehow, must tell the callee that it is not returning a meaningful value.
|
||||
</p>
|
||||
<p>
|
||||
A similar situation occurs with function (C): it is conceptually an error to
|
||||
ask a <span class="emphasis"><em>null-area</em></span> polygon to return a point inside itself,
|
||||
but in many applications, it is just impractical for performance reasons to
|
||||
treat this as an error (because detecting that the polygon has no area might
|
||||
be too expensive to be required to be tested previously), and either an arbitrary
|
||||
point (typically at infinity) is returned, or some efficient way to tell the
|
||||
callee that there is no such point is used.
|
||||
</p>
|
||||
<p>
|
||||
There are various mechanisms to let functions communicate that the returned
|
||||
value is not valid. One such mechanism, which is quite common since it has
|
||||
zero or negligible overhead, is to use a special value which is reserved to
|
||||
communicate this. Classical examples of such special values are <code class="computeroutput"><span class="identifier">EOF</span></code>, <code class="computeroutput"><span class="identifier">string</span><span class="special">::</span><span class="identifier">npos</span></code>, points
|
||||
at infinity, etc...
|
||||
</p>
|
||||
<p>
|
||||
When those values exist, i.e. the return type can hold all meaningful values
|
||||
<span class="emphasis"><em>plus</em></span> the <span class="emphasis"><em>signal</em></span> value, this mechanism
|
||||
is quite appropriate and well known. Unfortunately, there are cases when such
|
||||
values do not exist. In these cases, the usual alternative is either to use
|
||||
a wider type, such as <code class="computeroutput"><span class="keyword">int</span></code> in place
|
||||
of <code class="computeroutput"><span class="keyword">char</span></code>; or a compound type, such
|
||||
as <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">point</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span></code>.
|
||||
</p>
|
||||
<p>
|
||||
Returning a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span></code>, thus attaching a boolean flag to the result
|
||||
which indicates if the result is meaningful, has the advantage that can be
|
||||
turned into a consistent idiom since the first element of the pair can be whatever
|
||||
the function would conceptually return. For example, the last two functions
|
||||
could have the following interface:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="keyword">char</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span> <span class="identifier">get_async_input</span><span class="special">();</span>
|
||||
<span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">point</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span> <span class="identifier">polygon</span><span class="special">::</span><span class="identifier">get_any_point_effectively_inside</span><span class="special">();</span>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">readInt</span><span class="special">();</span> <span class="comment">// this function may return either an int or a not-an-int</span>
|
||||
|
||||
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">oi</span> <span class="special">=</span> <span class="identifier">readInt</span><span class="special">())</span> <span class="comment">// did I get a real int</span>
|
||||
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"my int is: "</span> <span class="special"><<</span> <span class="special">*</span><span class="identifier">oi</span><span class="special">;</span> <span class="comment">// use my int</span>
|
||||
<span class="keyword">else</span>
|
||||
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"I have no int"</span><span class="special">;</span>
|
||||
</pre>
|
||||
<p>
|
||||
These functions use a consistent interface for dealing with possibly nonexistent
|
||||
results:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">point</span><span class="special">,</span><span class="keyword">bool</span><span class="special">></span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">poly</span><span class="special">.</span><span class="identifier">get_any_point_effectively_inside</span><span class="special">();</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span> <span class="identifier">p</span><span class="special">.</span><span class="identifier">second</span> <span class="special">)</span>
|
||||
<span class="identifier">flood_fill</span><span class="special">(</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">first</span><span class="special">);</span>
|
||||
</pre>
|
||||
<p>
|
||||
However, not only is this quite a burden syntactically, it is also error prone
|
||||
since the user can easily use the function result (first element of the pair)
|
||||
without ever checking if it has a valid value.
|
||||
</p>
|
||||
<p>
|
||||
Clearly, we need a better idiom.
|
||||
</p>
|
||||
</div>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"><p><small>Last revised: April 11, 2014 at 13:25:26 GMT</small></p></td>
|
||||
<td align="left"><p><small>Last revised: May 08, 2014 at 12:05:10 GMT</small></p></td>
|
||||
<td align="right"><div class="copyright-footer"></div></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav"><a accesskey="n" href="boost_optional/development.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a></div>
|
||||
<div class="spirit-nav"><a accesskey="n" href="boost_optional/motivation.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a></div>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@ -1,26 +0,0 @@
|
||||
[/
|
||||
Boost.Optional
|
||||
|
||||
Copyright (c) 2003-2007 Fernando Luis Cacciola Carballal
|
||||
|
||||
Distributed under the Boost Software License, Version 1.0.
|
||||
(See accompanying file LICENSE_1_0.txt or copy at
|
||||
http://www.boost.org/LICENSE_1_0.txt)
|
||||
]
|
||||
|
||||
|
||||
|
||||
[section Implementation Notes]
|
||||
|
||||
`optional<T>` is currently implemented using a custom aligned storage facility
|
||||
built from `alignment_of` and `type_with_alignment` (both from Type Traits). It
|
||||
uses a separate boolean flag to indicate the initialization state.
|
||||
Placement new with `T`'s copy constructor and `T`'s destructor are explicitly used
|
||||
to initialize,copy and destroy optional values.
|
||||
As a result, `T`'s default constructor is effectively by-passed, but the exception
|
||||
guarantees are basic.
|
||||
It is planned to replace the current implementation with another with stronger
|
||||
exception safety, such as a future `boost::variant`.
|
||||
|
||||
[endsect]
|
||||
|
||||
80
doc/motivation.qbk
Normal file
80
doc/motivation.qbk
Normal file
@ -0,0 +1,80 @@
|
||||
[/
|
||||
Boost.Optional
|
||||
|
||||
Copyright (c) 2003-2007 Fernando Luis Cacciola Carballal
|
||||
Copyright (c) 2014 Andrzej Krzemienski
|
||||
|
||||
Distributed under the Boost Software License, Version 1.0.
|
||||
(See accompanying file LICENSE_1_0.txt or copy at
|
||||
http://www.boost.org/LICENSE_1_0.txt)
|
||||
]
|
||||
|
||||
[section Motivation]
|
||||
|
||||
Consider these functions which should return a value but which might not have
|
||||
a value to return:
|
||||
|
||||
* (A) `double sqrt(double n );`
|
||||
* (B) `char get_async_input();`
|
||||
* (C) `point polygon::get_any_point_effectively_inside();`
|
||||
|
||||
There are different approaches to the issue of not having a value to return.
|
||||
|
||||
A typical approach is to consider the existence of a valid return value as a
|
||||
postcondition, so that if the function cannot compute the value to return, it
|
||||
has either undefined behavior (and can use assert in a debug build) or uses a
|
||||
runtime check and throws an exception if the postcondition is violated. This
|
||||
is a reasonable choice for example, for function (A), because the lack of a
|
||||
proper return value is directly related to an invalid parameter (out of domain
|
||||
argument), so it is appropriate to require the callee to supply only parameters
|
||||
in a valid domain for execution to continue normally.
|
||||
|
||||
However, function (B), because of its asynchronous nature, does not fail just
|
||||
because it can't find a value to return; so it is incorrect to consider such
|
||||
a situation an error and assert or throw an exception. This function must
|
||||
return, and somehow, must tell the callee that it is not returning a meaningful
|
||||
value.
|
||||
|
||||
A similar situation occurs with function (C): it is conceptually an error to
|
||||
ask a ['null-area] polygon to return a point inside itself, but in many
|
||||
applications, it is just impractical for performance reasons to treat this as
|
||||
an error (because detecting that the polygon has no area might be too expensive
|
||||
to be required to be tested previously), and either an arbitrary point
|
||||
(typically at infinity) is returned, or some efficient way to tell the callee
|
||||
that there is no such point is used.
|
||||
|
||||
There are various mechanisms to let functions communicate that the returned
|
||||
value is not valid. One such mechanism, which is quite common since it has
|
||||
zero or negligible overhead, is to use a special value which is reserved to
|
||||
communicate this. Classical examples of such special values are `EOF`,
|
||||
`string::npos`, points at infinity, etc...
|
||||
|
||||
When those values exist, i.e. the return type can hold all meaningful values
|
||||
['plus] the ['signal] value, this mechanism is quite appropriate and well known.
|
||||
Unfortunately, there are cases when such values do not exist. In these cases,
|
||||
the usual alternative is either to use a wider type, such as `int` in place of
|
||||
`char`; or a compound type, such as `std::pair<point,bool>`.
|
||||
|
||||
Returning a `std::pair<T,bool>`, thus attaching a boolean flag to the result
|
||||
which indicates if the result is meaningful, has the advantage that can be
|
||||
turned into a consistent idiom since the first element of the pair can be
|
||||
whatever the function would conceptually return. For example, the last two
|
||||
functions could have the following interface:
|
||||
|
||||
std::pair<char,bool> get_async_input();
|
||||
std::pair<point,bool> polygon::get_any_point_effectively_inside();
|
||||
|
||||
These functions use a consistent interface for dealing with possibly nonexistent
|
||||
results:
|
||||
|
||||
std::pair<point,bool> p = poly.get_any_point_effectively_inside();
|
||||
if ( p.second )
|
||||
flood_fill(p.first);
|
||||
|
||||
However, not only is this quite a burden syntactically, it is also error prone
|
||||
since the user can easily use the function result (first element of the pair)
|
||||
without ever checking if it has a valid value.
|
||||
|
||||
Clearly, we need a better idiom.
|
||||
|
||||
[endsect]
|
||||
@ -2,6 +2,7 @@
|
||||
[quickbook 1.4]
|
||||
[authors [Cacciola Carballal, Fernando Luis]]
|
||||
[copyright 2003-2007 Fernando Luis Cacciola Carballal]
|
||||
[copyright 2014 Andrzej Krzemieński]
|
||||
[category miscellaneous]
|
||||
[id optional]
|
||||
[dirname optional]
|
||||
@ -44,82 +45,23 @@ Distributed under the Boost Software License, Version 1.0.
|
||||
[def __GO_TO__ [$images/callouts/R.png]]
|
||||
|
||||
|
||||
[section Motivation]
|
||||
[section Introduction]
|
||||
This library can be used to represent 'optional' (or 'nullable') objects that can be safely passed by value:
|
||||
|
||||
Consider these functions which should return a value but which might not have
|
||||
a value to return:
|
||||
|
||||
* (A) `double sqrt(double n );`
|
||||
* (B) `char get_async_input();`
|
||||
* (C) `point polygon::get_any_point_effectively_inside();`
|
||||
|
||||
There are different approaches to the issue of not having a value to return.
|
||||
|
||||
A typical approach is to consider the existence of a valid return value as a
|
||||
postcondition, so that if the function cannot compute the value to return, it
|
||||
has either undefined behavior (and can use assert in a debug build) or uses a
|
||||
runtime check and throws an exception if the postcondition is violated. This
|
||||
is a reasonable choice for example, for function (A), because the lack of a
|
||||
proper return value is directly related to an invalid parameter (out of domain
|
||||
argument), so it is appropriate to require the callee to supply only parameters
|
||||
in a valid domain for execution to continue normally.
|
||||
|
||||
However, function (B), because of its asynchronous nature, does not fail just
|
||||
because it can't find a value to return; so it is incorrect to consider such
|
||||
a situation an error and assert or throw an exception. This function must
|
||||
return, and somehow, must tell the callee that it is not returning a meaningful
|
||||
value.
|
||||
|
||||
A similar situation occurs with function (C): it is conceptually an error to
|
||||
ask a ['null-area] polygon to return a point inside itself, but in many
|
||||
applications, it is just impractical for performance reasons to treat this as
|
||||
an error (because detecting that the polygon has no area might be too expensive
|
||||
to be required to be tested previously), and either an arbitrary point
|
||||
(typically at infinity) is returned, or some efficient way to tell the callee
|
||||
that there is no such point is used.
|
||||
|
||||
There are various mechanisms to let functions communicate that the returned
|
||||
value is not valid. One such mechanism, which is quite common since it has
|
||||
zero or negligible overhead, is to use a special value which is reserved to
|
||||
communicate this. Classical examples of such special values are `EOF`,
|
||||
`string::npos`, points at infinity, etc...
|
||||
|
||||
When those values exist, i.e. the return type can hold all meaningful values
|
||||
['plus] the ['signal] value, this mechanism is quite appropriate and well known.
|
||||
Unfortunately, there are cases when such values do not exist. In these cases,
|
||||
the usual alternative is either to use a wider type, such as `int` in place of
|
||||
`char`; or a compound type, such as `std::pair<point,bool>`.
|
||||
|
||||
Returning a `std::pair<T,bool>`, thus attaching a boolean flag to the result
|
||||
which indicates if the result is meaningful, has the advantage that can be
|
||||
turned into a consistent idiom since the first element of the pair can be
|
||||
whatever the function would conceptually return. For example, the last two
|
||||
functions could have the following interface:
|
||||
|
||||
std::pair<char,bool> get_async_input();
|
||||
std::pair<point,bool> polygon::get_any_point_effectively_inside();
|
||||
|
||||
These functions use a consistent interface for dealing with possibly nonexistent
|
||||
results:
|
||||
|
||||
std::pair<point,bool> p = poly.get_any_point_effectively_inside();
|
||||
if ( p.second )
|
||||
flood_fill(p.first);
|
||||
|
||||
However, not only is this quite a burden syntactically, it is also error prone
|
||||
since the user can easily use the function result (first element of the pair)
|
||||
without ever checking if it has a valid value.
|
||||
|
||||
Clearly, we need a better idiom.
|
||||
optional<int> readInt(); // this function may return either an int or a not-an-int
|
||||
|
||||
if (optional<int> oi = readInt()) // did I get a real int
|
||||
cout << "my int is: " << *oi; // use my int
|
||||
else
|
||||
cout << "I have no int";
|
||||
|
||||
[endsect]
|
||||
|
||||
|
||||
[include motivation.qbk]
|
||||
[include development.qbk]
|
||||
[include reference.qbk]
|
||||
[include examples.qbk]
|
||||
[include special_cases.qbk]
|
||||
[include implementation_notes.qbk]
|
||||
[include dependencies.qbk]
|
||||
[include acknowledgments.qbk]
|
||||
|
||||
|
||||
@ -22,30 +22,42 @@
|
||||
|
||||
// (If T is of reference type, the parameters and results by reference are by value)
|
||||
|
||||
optional () ; ``[link reference_optional_constructor __GO_TO__]``
|
||||
optional () noexcept ; ``[link reference_optional_constructor __GO_TO__]``
|
||||
|
||||
optional ( none_t ) ; ``[link reference_optional_constructor_none_t __GO_TO__]``
|
||||
optional ( none_t ) noexcept ; ``[link reference_optional_constructor_none_t __GO_TO__]``
|
||||
|
||||
optional ( T const& v ) ; ``[link reference_optional_constructor_value __GO_TO__]``
|
||||
|
||||
optional ( T&& v ) ; ``[link reference_optional_constructor_move_value __GO_TO__]``
|
||||
|
||||
// [new in 1.34]
|
||||
optional ( bool condition, T const& v ) ; ``[link reference_optional_constructor_bool_value __GO_TO__]``
|
||||
|
||||
optional ( optional const& rhs ) ; ``[link reference_optional_constructor_optional __GO_TO__]``
|
||||
|
||||
optional ( optional&& rhs ) noexcept(``['see below]``) ; ``[link reference_optional_move_constructor_optional __GO_TO__]``
|
||||
|
||||
template<class U> explicit optional ( optional<U> const& rhs ) ; ``[link reference_optional_constructor_other_optional __GO_TO__]``
|
||||
|
||||
template<class U> explicit optional ( optional<U>&& rhs ) ; ``[link reference_optional_move_constructor_other_optional __GO_TO__]``
|
||||
|
||||
template<class InPlaceFactory> explicit optional ( InPlaceFactory const& f ) ; ``[link reference_optional_constructor_factory __GO_TO__]``
|
||||
|
||||
template<class TypedInPlaceFactory> explicit optional ( TypedInPlaceFactory const& f ) ; ``[link reference_optional_constructor_factory __GO_TO__]``
|
||||
|
||||
optional& operator = ( none_t ) ; ``[/[link reference_optional_operator_equal_none_t __GO_TO__]]``
|
||||
optional& operator = ( none_t ) noexcept ; ``[link reference_optional_operator_equal_none_t __GO_TO__]``
|
||||
|
||||
optional& operator = ( T const& v ) ; ``[link reference_optional_operator_equal_value __GO_TO__]``
|
||||
|
||||
optional& operator = ( T&& v ) ; ``[link reference_optional_operator_move_equal_value __GO_TO__]``
|
||||
|
||||
optional& operator = ( optional const& rhs ) ; ``[link reference_optional_operator_equal_optional __GO_TO__]``
|
||||
|
||||
optional& operator = ( optional&& rhs ) noexcept(``['see below]``) ; ``[link reference_optional_operator_move_equal_optional __GO_TO__]``
|
||||
|
||||
template<class U> optional& operator = ( optional<U> const& rhs ) ; ``[link reference_optional_operator_equal_other_optional __GO_TO__]``
|
||||
|
||||
template<class U> optional& operator = ( optional<U>&& rhs ) ; ``[link reference_optional_operator_move_equal_other_optional __GO_TO__]``
|
||||
|
||||
template<class InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ; ``[link reference_optional_operator_equal_factory __GO_TO__]``
|
||||
|
||||
@ -66,14 +78,14 @@
|
||||
T const* get_ptr() const ; ``[link reference_optional_get_ptr __GO_TO__]``
|
||||
T* get_ptr() ; ``[link reference_optional_get_ptr __GO_TO__]``
|
||||
|
||||
operator unspecified-bool-type() const ; ``[link reference_optional_operator_bool __GO_TO__]``
|
||||
explicit operator bool() const ; ``[link reference_optional_operator_bool __GO_TO__]``
|
||||
|
||||
bool operator!() const ; ``[link reference_optional_operator_not __GO_TO__]``
|
||||
bool operator!() const noexcept ; ``[link reference_optional_operator_not __GO_TO__]``
|
||||
|
||||
// deprecated methods
|
||||
|
||||
// (deprecated)
|
||||
void reset() ; ``[link reference_optional_reset __GO_TO__]``
|
||||
void reset() noexcept ; ``[link reference_optional_reset __GO_TO__]``
|
||||
|
||||
// (deprecated)
|
||||
void reset ( T const& ) ; ``[link reference_optional_reset_value __GO_TO__]``
|
||||
@ -94,6 +106,10 @@
|
||||
template<class T> inline bool operator <= ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_less_or_equal_optional_optional __GO_TO__]``
|
||||
|
||||
template<class T> inline bool operator >= ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_greater_or_equal_optional_optional __GO_TO__]``
|
||||
|
||||
template<class T> inline bool operator == ( optional<T> const& x, none_t ) noexcept ; ``[link reference_operator_compare_equal_optional_none __GO_TO__]``
|
||||
|
||||
template<class T> inline bool operator != ( optional<T> const& x, none_t ) noexcept ; ``[link reference_operator_compare_not_equal_optional_none __GO_TO__]``
|
||||
|
||||
// [new in 1.34]
|
||||
template<class T> inline optional<T> make_optional ( T const& v ) ; ``[link reference_make_optional_value __GO_TO__]``
|
||||
@ -151,12 +167,11 @@ __SPACE__
|
||||
|
||||
[#reference_optional_constructor]
|
||||
|
||||
[: `optional<T>::optional();`]
|
||||
[: `optional<T>::optional() noexcept;`]
|
||||
|
||||
* [*Effect:] Default-Constructs an `optional`.
|
||||
* [*Postconditions:] `*this` is [_uninitialized].
|
||||
* [*Throws:] Nothing.
|
||||
* Notes: T's default constructor [_is not] called.
|
||||
* [*Notes:] T's default constructor [_is not] called.
|
||||
* [*Example:]
|
||||
``
|
||||
optional<T> def ;
|
||||
@ -167,11 +182,10 @@ __SPACE__
|
||||
|
||||
[#reference_optional_constructor_none_t]
|
||||
|
||||
[: `optional<T>::optional( none_t );`]
|
||||
[: `optional<T>::optional( none_t ) noexcept;`]
|
||||
|
||||
* [*Effect:] Constructs an `optional` uninitialized.
|
||||
* [*Postconditions:] `*this` is [_uninitialized].
|
||||
* [*Throws:] Nothing.
|
||||
* [*Notes:] `T`'s default constructor [_is not] called. The expression
|
||||
`boost::none` denotes an instance of `boost::none_t` that can be used as
|
||||
the parameter.
|
||||
@ -188,8 +202,9 @@ __SPACE__
|
||||
|
||||
[: `optional<T `['(not a ref)]`>::optional( T const& v )`]
|
||||
|
||||
* [*Requires:] `is_copy_constructible<T>::value` is `true`.
|
||||
* [*Effect:] Directly-Constructs an `optional`.
|
||||
* [*Postconditions:] `*this` is [_initialized] and its value is a['copy]
|
||||
* [*Postconditions:] `*this` is [_initialized] and its value is a ['copy]
|
||||
of `v`.
|
||||
* [*Throws:] Whatever `T::T( T const& )` throws.
|
||||
* [*Notes: ] `T::T( T const& )` is called.
|
||||
@ -220,6 +235,33 @@ assert ( *opt == v ) ;
|
||||
assert (*opt == v);
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_constructor_move_value]
|
||||
|
||||
[: `optional<T `['(not a ref)]`>::optional( T&& v )`]
|
||||
|
||||
* [*Requires:] `is_move_constructible<T>::value` is `true`.
|
||||
* [*Effect:] Directly-Move-Constructs an `optional`.
|
||||
* [*Postconditions:] `*this` is [_initialized] and its value is move-constructed from `v`.
|
||||
* [*Throws:] Whatever `T::T( T&& )` throws.
|
||||
* [*Notes: ] `T::T( T&& )` is called.
|
||||
* [*Exception Safety:] Exceptions can only be thrown during
|
||||
`T::T( T&& );` in that case, the state of `v` is determined by exception safety guarantees for `T::T(T&&)`.
|
||||
* [*Example:]
|
||||
``
|
||||
T v1, v2;
|
||||
optional<T> opt(std::move(v1));
|
||||
assert ( *opt == v2 ) ;
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[: `optional<T&>::optional( T&& ref ) = delete`]
|
||||
|
||||
* [*Notes:] This constructor is deleted
|
||||
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_constructor_bool_value]
|
||||
@ -243,6 +285,7 @@ __SPACE__
|
||||
|
||||
[: `optional<T `['(not a ref)]`>::optional( optional const& rhs );`]
|
||||
|
||||
* [*Requires:] `is_copy_constructible<T>::value` is `true`.
|
||||
* [*Effect:] Copy-Constructs an `optional`.
|
||||
* [*Postconditions:] If rhs is initialized, `*this` is initialized and
|
||||
its value is a ['copy] of the value of `rhs`; else `*this` is uninitialized.
|
||||
@ -299,6 +342,70 @@ assert ( *init2 == 3 ) ;
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_move_constructor_optional]
|
||||
|
||||
[: `optional<T `['(not a ref)]`>::optional( optional&& rhs ) noexcept(`['see below]`);`]
|
||||
|
||||
* [*Requires:] `is_move_constructible<T>::value` is `true`.
|
||||
* [*Effect:] Move-constructs an `optional`.
|
||||
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and
|
||||
its value is move constructed from `rhs`; else `*this` is uninitialized.
|
||||
* [*Throws:] Whatever `T::T( T&& )` throws.
|
||||
* [*Notes:] If `rhs` is initialized, `T::T( T && )` is called. The expression inside `noexcept` is equivalent to `is_nothrow_move_constructible<T>::value`.
|
||||
* [*Exception Safety:] Exceptions can only be thrown during
|
||||
`T::T( T&& );` in that case, `rhs` remains initialized and the value of `*rhs` is determined by exception safety of `T::T(T&&)`.
|
||||
* [*Example:]
|
||||
``
|
||||
optional<std::unique_ptr<T>> uninit ;
|
||||
assert (!uninit);
|
||||
|
||||
optional<std::unique_ptr<T>> uinit2 ( std::move(uninit) ) ;
|
||||
assert ( uninit2 == uninit );
|
||||
|
||||
optional<std::unique_ptr<T>> init( std::uniqye_ptr<T>(new T(2)) );
|
||||
assert ( **init == T(2) ) ;
|
||||
|
||||
optional<std::unique_ptr<T>> init2 ( std::move(init) ) ;
|
||||
assert ( init );
|
||||
assert ( *init == nullptr );
|
||||
assert ( init2 );
|
||||
assert ( **init2 == T(2) ) ;
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[: `optional<T&>::optional( optional && rhs );`]
|
||||
|
||||
* [*Effect:] Move-Constructs an `optional`.
|
||||
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and its
|
||||
value is another reference to the same object referenced by `*rhs`; else
|
||||
`*this` is uninitialized.
|
||||
* [*Throws:] Nothing.
|
||||
* [*Notes:] If `rhs` is initialized, both `*this` and `*rhs` will reefer to the
|
||||
same object (they alias).
|
||||
* [*Example:]
|
||||
``
|
||||
optional<std::unique_ptr<T>&> uninit ;
|
||||
assert (!uninit);
|
||||
|
||||
optional<std::unique_ptr<T>&> uinit2 ( std::move(uninit) ) ;
|
||||
assert ( uninit2 == uninit );
|
||||
|
||||
std::unique_ptr<T> v(new T(2)) ;
|
||||
optional<std::unique_ptr<T>&> init(v);
|
||||
assert ( *init == v ) ;
|
||||
|
||||
optional<std::unique_ptr<T>&> init2 ( std::move(init) ) ;
|
||||
assert ( *init2 == v ) ;
|
||||
|
||||
*v = 3 ;
|
||||
|
||||
assert ( **init == 3 ) ;
|
||||
assert ( **init2 == 3 ) ;
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_constructor_other_optional]
|
||||
|
||||
[: `template<U> explicit optional<T` ['(not a ref)]`>::optional( optional<U> const& rhs );`]
|
||||
@ -323,6 +430,30 @@ assert( *y == 123 ) ;
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_move_constructor_other_optional]
|
||||
|
||||
[: `template<U> explicit optional<T` ['(not a ref)]`>::optional( optional<U>&& rhs );`]
|
||||
|
||||
* [*Effect:] Move-constructs an `optional`.
|
||||
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and its
|
||||
value is move constructed from `*rhs`; else `*this` is
|
||||
uninitialized.
|
||||
* [*Throws:] Whatever `T::T( U&& )` throws.
|
||||
* [*Notes: ] `T::T( U&& )` is called if `rhs` is initialized, which requires a
|
||||
valid conversion from `U` to `T`.
|
||||
* [*Exception Safety:] Exceptions can only be thrown during `T::T( U&& );`
|
||||
in that case, `rhs` remains initialized and the value of `*rhs` is determined by exception safety guarantee of `T::T( U&& )`.
|
||||
* [*Example:]
|
||||
``
|
||||
optional<double> x(123.4);
|
||||
assert ( *x == 123.4 ) ;
|
||||
|
||||
optional<int> y(std::move(x)) ;
|
||||
assert( *y == 123 ) ;
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_constructor_factory]
|
||||
|
||||
[: `template<InPlaceFactory> explicit optional<T` ['(not a ref)]`>::optional( InPlaceFactory const& f );`]
|
||||
@ -352,6 +483,15 @@ assert ( *y == v ) ;
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_operator_equal_none_t]
|
||||
|
||||
[: `optional& optional<T>::operator= ( none_t ) noexcept;`]
|
||||
|
||||
* [*Effect:] If `*this` is initialized destroys its contained value.
|
||||
* [*Postconditions: ] `*this` is uninitialized.
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_operator_equal_value]
|
||||
|
||||
[: `optional& optional<T` ['(not a ref)]`>::operator= ( T const& rhs ) ;`]
|
||||
@ -408,6 +548,42 @@ c = 4 ;
|
||||
assert ( *opt == 4 ) ;
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_operator_move_equal_value]
|
||||
|
||||
[: `optional& optional<T` ['(not a ref)]`>::operator= ( T&& rhs ) ;`]
|
||||
|
||||
* [*Effect:] Moves the value `rhs` to an `optional`.
|
||||
* [*Postconditions: ] `*this` is initialized and its value is moved from `rhs`.
|
||||
* [*Throws:] Whatever `T::operator=( T&& )` or `T::T(T &&)` throws.
|
||||
* [*Notes:] If `*this` was initialized, `T`'s move-assignment operator is used,
|
||||
otherwise, its move-constructor is used.
|
||||
* [*Exception Safety:] In the event of an exception, the initialization
|
||||
state of `*this` is unchanged and its value unspecified as far as `optional`
|
||||
is concerned (it is up to `T`'s `operator=()`). If `*this` is initially
|
||||
uninitialized and `T`'s ['move constructor] fails, `*this` is left properly
|
||||
uninitialized.
|
||||
* [*Example:]
|
||||
``
|
||||
T x;
|
||||
optional<T> def ;
|
||||
optional<T> opt(x) ;
|
||||
|
||||
T y1, y2, yR;
|
||||
def = std::move(y1) ;
|
||||
assert ( *def == yR ) ;
|
||||
opt = std::move(y2) ;
|
||||
assert ( *opt == yR ) ;
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[: `optional<T&>& optional<T&>::operator= ( T&& rhs ) = delete;`]
|
||||
|
||||
* [*Notes:] This assignment operator is deleted.
|
||||
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_operator_equal_optional]
|
||||
@ -471,6 +647,42 @@ assert ( *ora == 4 ) ;
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_operator_move_equal_optional]
|
||||
|
||||
[: `optional& optional<T` ['(not a ref)]`>::operator= ( optional&& rhs ) noexcept(`['see below]`);`]
|
||||
|
||||
* [*Effect:] Move-assigns another `optional` to an `optional`.
|
||||
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and
|
||||
its value is moved from `*rhs`, `rhs` remains initialized; else `*this` is uninitialized.
|
||||
* [*Throws:] Whatever `T::operator( T&& )` or `T::T( T && )` throws.
|
||||
* [*Notes:] If both `*this` and `rhs` are initially initialized, `T`'s
|
||||
['move assignment operator] is used. If `*this` is initially initialized but `rhs` is
|
||||
uninitialized, `T`'s [destructor] is called. If `*this` is initially uninitialized
|
||||
but `rhs` is initialized, `T`'s ['move constructor] is called. The expression inside `noexcept` is equivalent to `is_nothrow_move_constructible<T>::value && is_nothrow_move_assignable<T>::value`.
|
||||
* [*Exception Safety:] In the event of an exception, the initialization state of
|
||||
`*this` is unchanged and its value unspecified as far as optional is concerned
|
||||
(it is up to `T`'s `operator=()`). If `*this` is initially uninitialized and
|
||||
`T`'s ['move constructor] fails, `*this` is left properly uninitialized.
|
||||
* [*Example:]
|
||||
``
|
||||
optional<T> opt(T(2)) ;
|
||||
optional<T> def ;
|
||||
|
||||
opt = def ;
|
||||
assert ( def ) ;
|
||||
assert ( opt ) ;
|
||||
assert ( *opt == T(2) ) ;
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[: `optional<T&> & optional<T&>::operator= ( optional<T&>&& rhs ) ;`]
|
||||
|
||||
* [*Effect:] Same as `optional<T&>::operator= ( optional<T&> const& rhs )`.
|
||||
|
||||
__SPACE__
|
||||
|
||||
|
||||
[#reference_optional_operator_equal_other_optional]
|
||||
|
||||
[: `template<U> optional& optional<T` ['(not a ref)]`>::operator= ( optional<U> const& rhs ) ;`]
|
||||
@ -502,6 +714,37 @@ assert ( *opt1 == static_cast<U>(v) ) ;
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_operator_move_equal_other_optional]
|
||||
|
||||
[: `template<U> optional& optional<T` ['(not a ref)]`>::operator= ( optional<U>&& rhs ) ;`]
|
||||
|
||||
* [*Effect:] Move-assigns another convertible optional to an optional.
|
||||
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and
|
||||
its value is moved from the value of `rhs`; else
|
||||
`*this` is uninitialized.
|
||||
* [*Throws:] Whatever `T::operator=( U&& )` or `T::T( U&& )` throws.
|
||||
* [*Notes:] If both `*this` and `rhs` are initially initialized, `T`'s
|
||||
[' assignment operator] (from `U&&`) is used. If `*this` is initially initialized
|
||||
but `rhs` is uninitialized, `T`'s ['destructor] is called. If `*this` is
|
||||
initially uninitialized but `rhs` is initialized, `T`'s ['converting constructor]
|
||||
(from `U&&`) is called.
|
||||
* [*Exception Safety:] In the event of an exception, the initialization state
|
||||
of `*this` is unchanged and its value unspecified as far as optional is
|
||||
concerned (it is up to `T`'s `operator=()`). If `*this` is initially
|
||||
uninitialized and `T`'s converting constructor fails, `*this` is left properly
|
||||
uninitialized.
|
||||
* [*Example:]
|
||||
``
|
||||
T v;
|
||||
optional<T> opt0(v);
|
||||
optional<U> opt1;
|
||||
|
||||
opt1 = std::move(opt0) ;
|
||||
assert ( *opt1 == static_cast<U>(v) ) ;
|
||||
``
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_optional_operator_equal_factory]
|
||||
|
||||
[: `template<InPlaceFactory> optional<T>& optional<T` ['(not a ref)]`>::operator=( InPlaceFactory const& f );`]
|
||||
@ -528,7 +771,7 @@ __SPACE__
|
||||
|
||||
[#reference_optional_reset]
|
||||
|
||||
[: `void optional<T>::reset() ;`]
|
||||
[: `void optional<T>::reset() noexcept ;`]
|
||||
* [*Deprecated:] Same as `operator=( detail::none_t );`
|
||||
|
||||
__SPACE__
|
||||
@ -543,7 +786,7 @@ __SPACE__
|
||||
[: `inline T const& get ( optional<T` ['(not a ref)]`> const& ) ;`]
|
||||
[: `inline T& get ( optional<T` ['(not a ref)]`> &) ;`]
|
||||
|
||||
* [*Requirements:] `*this` is initialized
|
||||
* [*Requires:] `*this` is initialized
|
||||
* [*Returns:] A reference to the contained value
|
||||
* [*Throws:] Nothing.
|
||||
* [*Notes:] The requirement is asserted via `BOOST_ASSERT()`.
|
||||
@ -593,7 +836,7 @@ __SPACE__
|
||||
[: `inline T const& get ( optional<T&> const& ) ;`]
|
||||
[: `inline T& get ( optional<T&> &) ;`]
|
||||
|
||||
* [*Requirements: ] `*this` is initialized
|
||||
* [*Requires: ] `*this` is initialized
|
||||
* [*Returns:] [_The] reference contained.
|
||||
* [*Throws:] Nothing.
|
||||
* [*Notes:] The requirement is asserted via `BOOST_ASSERT()`.
|
||||
@ -641,7 +884,7 @@ __SPACE__
|
||||
[: `T const* optional<T` ['(not a ref)]`>::operator ->() const ;`]
|
||||
[: `T* optional<T` ['(not a ref)]`>::operator ->() ;`]
|
||||
|
||||
* [*Requirements: ] `*this` is initialized.
|
||||
* [*Requires: ] `*this` is initialized.
|
||||
* [*Returns:] A pointer to the contained value.
|
||||
* [*Throws:] Nothing.
|
||||
* [*Notes:] The requirement is asserted via `BOOST_ASSERT()`.
|
||||
@ -657,11 +900,11 @@ __SPACE__
|
||||
|
||||
[#reference_optional_operator_bool]
|
||||
|
||||
[: `optional<T>::operator `['unspecified-bool-type]`() const ;`]
|
||||
[: `explicit optional<T>::operator bool() const ;`]
|
||||
|
||||
* [*Returns:] An unspecified value which if used on a boolean context
|
||||
is equivalent to (`get_ptr() != 0`)
|
||||
* [*Returns:] `get_ptr() != 0`.
|
||||
* [*Throws:] Nothing.
|
||||
* [*Notes:] On compilers that do not support explicit conversion operators this falls back to safe-bool idiom.
|
||||
* [*Example:]
|
||||
``
|
||||
optional<T> def ;
|
||||
@ -675,10 +918,9 @@ __SPACE__
|
||||
|
||||
[#reference_optional_operator_not]
|
||||
|
||||
[: `bool optional<T>::operator!() ;`]
|
||||
[: `bool optional<T>::operator!() noexcept ;`]
|
||||
|
||||
* [*Returns:] If `*this` is uninitialized, `true`; else `false`.
|
||||
* [*Throws:] Nothing.
|
||||
* [*Notes:] This operator is provided for those compilers which can't
|
||||
use the ['unspecified-bool-type operator] in certain boolean contexts.
|
||||
* [*Example:]
|
||||
@ -697,7 +939,7 @@ __SPACE__
|
||||
|
||||
[: `bool optional<T>::is_initialized() const ;`]
|
||||
|
||||
* [*Deprecated:] Same as `operator `['unspecified-bool-type]`() ;`
|
||||
* [*Deprecated:] Same as `explicit operator bool () ;`
|
||||
|
||||
__SPACE__
|
||||
|
||||
@ -743,6 +985,7 @@ __SPACE__
|
||||
|
||||
[: `bool operator == ( optional<T> const& x, optional<T> const& y );`]
|
||||
|
||||
* [*Requires:] `T` shall meet requirements of `EqualityComparable`.
|
||||
* [*Returns:] If both `x` and `y` are initialized, `(*x == *y)`. If only
|
||||
`x` or `y` is initialized, `false`. If both are uninitialized, `true`.
|
||||
* [*Throws:] Nothing.
|
||||
@ -782,6 +1025,7 @@ __SPACE__
|
||||
|
||||
[: `bool operator < ( optional<T> const& x, optional<T> const& y );`]
|
||||
|
||||
* [*Requires:] `T` shall meet requirements of `LessThanComparable`.
|
||||
* [*Returns:] If `y` is not initialized, `false`. If `y` is initialized
|
||||
and `x` is not initialized, `true`. If both `x` and `y` are initialized,
|
||||
`(*x < *y)`.
|
||||
@ -836,7 +1080,7 @@ __SPACE__
|
||||
|
||||
[: `bool operator <= ( optional<T> const& x, optional<T> const& y );`]
|
||||
|
||||
* [*Returns: ] `!( y<x );`
|
||||
* [*Returns: ] `!( y < x );`
|
||||
* [*Throws:] Nothing.
|
||||
|
||||
__SPACE__
|
||||
@ -848,25 +1092,42 @@ __SPACE__
|
||||
* [*Returns: ] `!( x<y );`
|
||||
* [*Throws:] Nothing.
|
||||
|
||||
[#reference_operator_compare_equal_optional_none]
|
||||
|
||||
[: `bool operator == ( optional<T> const& x, none_t ) noexcept;`]
|
||||
|
||||
* [*Returns:] `!x`.
|
||||
* [*Notes:] `T` need not meet requirements of `EqualityComparable`.
|
||||
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_operator_compare_not_equal_optional_none]
|
||||
|
||||
[: `bool operator != ( optional<T> const& x, none_t ) noexcept;`]
|
||||
|
||||
* [*Returns: ] `!( x == y );`
|
||||
|
||||
|
||||
__SPACE__
|
||||
|
||||
[#reference_swap_optional_optional]
|
||||
|
||||
[: `void swap ( optional<T>& x, optional<T>& y );`]
|
||||
[: `void swap ( optional<T>& x, optional<T>& y ) ;`]
|
||||
|
||||
* [*Effect:] If both `x` and `y` are initialized, calls `swap(*x,*y)`
|
||||
using `std::swap`. If only one is initialized, say `x`, calls:
|
||||
`y.reset(*x); x.reset();` If none is initialized, does nothing.
|
||||
* [*Postconditions:] The states of `x` and `y` interchanged.
|
||||
* [*Throws:] If both are initialized, whatever `swap(T&,T&)` throws. If only
|
||||
one is initialized, whatever `T::T ( T const& )` throws.
|
||||
one is initialized, whatever `T::T ( T&& )` throws.
|
||||
* [*Notes:] If both are initialized, `swap(T&,T&)` is used unqualified but
|
||||
with `std::swap` introduced in scope.
|
||||
If only one is initialized, `T::~T()` and `T::T( T const& )` is called.
|
||||
If only one is initialized, `T::~T()` and `T::T( T&& )` is called.
|
||||
* [*Exception Safety:] If both are initialized, this operation has the
|
||||
exception safety guarantees of `swap(T&,T&)`.
|
||||
If only one is initialized, it has the same basic guarantee as
|
||||
`optional<T>::reset( T const& )`.
|
||||
`optional<T>::operator= ( T&& )`.
|
||||
* [*Example:]
|
||||
``
|
||||
T x(12);
|
||||
|
||||
@ -17,10 +17,19 @@ Also, even though `optional<T&>` treats it wrapped pseudo-object much as
|
||||
a real value, a true real reference is stored so aliasing will ocurr:
|
||||
|
||||
* Copies of `optional<T&>` will copy the references but all these references
|
||||
will nonetheless reefer to the same object.
|
||||
will nonetheless refer to the same object.
|
||||
* Value-access will actually provide access to the referenced object
|
||||
rather than the reference itself.
|
||||
|
||||
[warning On compilers that do not conform to Standard C++ rules of reference binding, operations on optional references might give adverse results: rather than binding a reference to a designated object they may create an unexpected temporary and bind to it. For more details see [link boost_optional.dependencies_and_portability.optional_reference_binding Dependencies and Portability section].]
|
||||
|
||||
[heading Rvalue references]
|
||||
|
||||
Rvalue references and lvalue references to const have the ability in C++ to extend the life time of a temporary they bind to. Optional references do not have this capability, therefore to avoid surprising effects it is not possible to initialize an optional references from a temporary. Optional rvalue references are disabled altogether. Also, the initialization and assignment of an optional reference to const from rvalue reference is disabled.
|
||||
|
||||
const int& i = 1; // legal
|
||||
optional<const int&> oi = 1; // illegal
|
||||
|
||||
[endsect]
|
||||
|
||||
[section Rebinding semantics for assignment of optional references]
|
||||
@ -253,17 +262,17 @@ The factories are implemented in the headers: __IN_PLACE_FACTORY_HPP__ and __TYP
|
||||
|
||||
`optional<bool>` should be used with special caution and consideration.
|
||||
|
||||
First, it is functionally similar to a tristate boolean (false,maybe,true)
|
||||
First, it is functionally similar to a tristate boolean (false, maybe, true)
|
||||
—such as __BOOST_TRIBOOL__— except that in a tristate boolean, the maybe state
|
||||
[_represents a valid value], unlike the corresponding state of an uninitialized
|
||||
`optional<bool>`.
|
||||
It should be carefully considered if an `optional<bool>` instead of a `tribool`
|
||||
is really needed.
|
||||
|
||||
Second, `optional<>` provides an implicit conversion to `bool`. This
|
||||
conversion refers to the initialization state and not to the contained value.
|
||||
Using `optional<bool>` can lead to subtle errors due to the implicit `bool`
|
||||
conversion:
|
||||
Second, although `optional<>` provides a contextual conversion to `bool` in C++11,
|
||||
this falls back to an implicit conversion on older compilers. This conversion refers
|
||||
to the initialization state and not to the contained value. Using `optional<bool>`
|
||||
can lead to subtle errors due to the implicit `bool` conversion:
|
||||
|
||||
void foo ( bool v ) ;
|
||||
void bar()
|
||||
@ -280,90 +289,84 @@ The only implicit conversion is to `bool`, and it is safe in the sense that
|
||||
typical integral promotions don't apply (i.e. if `foo()` takes an `int`
|
||||
instead, it won't compile).
|
||||
|
||||
Third, mixed comparisons with `bool` work differently than similar mixed comparisons between pointers and `bool`, so the results might surprise you:
|
||||
|
||||
optional<bool> oEmpty(none), oTrue(true), oFalse(false);
|
||||
|
||||
if (oEmpty == none); // renders true
|
||||
if (oEmpty == false); // renders false!
|
||||
if (oEmpty == true); // renders false!
|
||||
|
||||
if (oFalse == none); // renders false
|
||||
if (oFalse == false); // renders true!
|
||||
if (oFalse == true); // renders false
|
||||
|
||||
if (oTrue == none); // renders false
|
||||
if (oTrue == false); // renders false
|
||||
if (oTrue == true); // renders true
|
||||
|
||||
In other words, for `optional<>`, the following assertion does not hold:
|
||||
|
||||
assert((opt == false) == (!opt));
|
||||
[endsect]
|
||||
|
||||
[section Exception Safety Guarantees]
|
||||
|
||||
Because of the current implementation (see [link boost_optional.implementation_notes Implementation Notes]), all of the assignment methods:
|
||||
This library assumes that `T`'s destructor does not throw exceptions. If it does, the behaviour of many operations on `optional<T>` is undefined.
|
||||
|
||||
The following mutating operations never throw exceptions:
|
||||
|
||||
* `optional<T>::operator= ( none_t ) noexcept`
|
||||
* `optional<T>::reset() noexcept`
|
||||
|
||||
In addition, the following constructors and the destructor never throw exceptions:
|
||||
|
||||
* `optional<T>::optional() noexcept`
|
||||
* `optional<T>::optional( none_t ) noexcept`
|
||||
|
||||
|
||||
Regarding the following assignment functions:
|
||||
|
||||
* `optional<T>::operator= ( optional<T> const& )`
|
||||
* `optional<T>::operator= ( T const& )`
|
||||
* `template<class U> optional<T>::operator= ( optional<U> const& )`
|
||||
* `template<class InPlaceFactory> optional<T>::operator= ( InPlaceFactory const& )`
|
||||
* `template<class TypedInPlaceFactory> optional<T>::operator= ( TypedInPlaceFactory const& ) `
|
||||
* `optional<T>::reset ( T const&)`
|
||||
* `optional<T>::reset( T const& )`
|
||||
|
||||
Can only ['guarantee] the [_basic exception safety]: The lvalue optional is
|
||||
left [_uninitialized] if an exception is thrown (any previous value is ['first]
|
||||
destroyed using `T::~T()`)
|
||||
They forward calls to the corresponding `T`'s constructors or assignments (depending on whether the optional object is initialized or not); so if both `T`'s constructor and the assignment provide strong exception safety guarantee, `optional<T>`'s assignment also provides strong exception safety guarantee; otherwise we only get the basic guarantee. Additionally, if both involved `T`'s constructor and the assignment never throw, `optional<T>`'s assignment also never throws.
|
||||
|
||||
On the other hand, the ['uninitializing] methods:
|
||||
Unless `T`'s constructor or assignment throws, `optional<T>` does not throw anything else on its own. A throw during assignment never changes the initialization state of any optional object involved:
|
||||
|
||||
* `optional<T>::operator= ( detail::none_t )`
|
||||
* `optional<T>::reset()`
|
||||
|
||||
Provide the no-throw guarantee (assuming a no-throw `T::~T()`)
|
||||
|
||||
However, since `optional<>` itself doesn't throw any exceptions, the only
|
||||
source for exceptions here are `T`'s constructor, so if you know the exception
|
||||
guarantees for `T::T ( T const& )`, you know that `optional`'s assignment and
|
||||
reset has the same guarantees.
|
||||
|
||||
//
|
||||
// Case 1: Exception thrown during assignment.
|
||||
//
|
||||
T v0(123);
|
||||
optional<T> opt0(v0);
|
||||
optional<T> opt1(val1);
|
||||
optional<T> opt2(val2);
|
||||
assert(opt1);
|
||||
assert(opt2);
|
||||
|
||||
try
|
||||
{
|
||||
T v1(456);
|
||||
optional<T> opt1(v1);
|
||||
opt0 = opt1 ;
|
||||
|
||||
// If no exception was thrown, assignment succeeded.
|
||||
assert( *opt0 == v1 ) ;
|
||||
opt1 = opt2; // throws
|
||||
}
|
||||
catch(...)
|
||||
{
|
||||
// If any exception was thrown, 'opt0' is reset to uninitialized.
|
||||
assert( !opt0 ) ;
|
||||
assert(opt1);
|
||||
assert(opt2);
|
||||
}
|
||||
|
||||
//
|
||||
// Case 2: Exception thrown during reset(v)
|
||||
//
|
||||
T v0(123);
|
||||
optional<T> opt(v0);
|
||||
try
|
||||
{
|
||||
T v1(456);
|
||||
opt.reset ( v1 ) ;
|
||||
|
||||
// If no exception was thrown, reset succeeded.
|
||||
assert( *opt == v1 ) ;
|
||||
}
|
||||
catch(...)
|
||||
{
|
||||
// If any exception was thrown, 'opt' is reset to uninitialized.
|
||||
assert( !opt ) ;
|
||||
}
|
||||
This also applies to move assignments/constructors. However, move operations are made no-throw more often.
|
||||
|
||||
[heading Swap]
|
||||
|
||||
`void swap( optional<T>&, optional<T>& )` has the same exception guarantee
|
||||
as `swap(T&,T&)` when both optionals are initialized.
|
||||
If only one of the optionals is initialized, it gives the same ['basic]
|
||||
exception guarantee as `optional<T>::reset( T const& )` (since
|
||||
`optional<T>::reset()` doesn't throw).
|
||||
If none of the optionals is initialized, it has no-throw guarantee
|
||||
since it is a no-op.
|
||||
Unless `swap` on optional is customized, its primary implementation forwards calls to `T`'s `swap` or move constructor (depending on the initialization state of the optional objects). Thus, if both `T`'s `swap` and move constructor never throw, `swap` on `optional<T>` never throws. similarly, if both `T`'s `swap` and move constructor offer strong guarantee, `swap` on `optional<T>` also offers a strong guarantee.
|
||||
|
||||
In case `swap` on optional is customized, the call to `T`'s move constructor are replaced with the calls to `T`'s default constructor followed by `swap`. (This is more useful on older compilers that do not support move semantics, when one wants to acheive stronger exception safety guarantees.) In this case the exception safety guarantees for `swap` are reliant on the guarantees of `T`'s `swap` and default constructor
|
||||
[endsect]
|
||||
|
||||
[section Type requirements]
|
||||
|
||||
In general, `T` must be __COPY_CONSTRUCTIBLE__ and have a no-throw destructor.
|
||||
The copy-constructible requirement is not needed if [*InPlaceFactories] are used.
|
||||
In general, `T` must be `MoveConstructible` and have a no-throw destructor.
|
||||
The `MoveConstructible` requirement is not needed if [*InPlaceFactories] are used.
|
||||
|
||||
`T` [_is not] required to be __SGI_DEFAULT_CONSTRUCTIBLE__.
|
||||
|
||||
|
||||
@ -1,4 +1,5 @@
|
||||
// Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
|
||||
// Copyright (C) 2014 Andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
@ -11,6 +12,7 @@
|
||||
//
|
||||
// Revisions:
|
||||
// 27 Apr 2008 (improved swap) Fernando Cacciola, Niels Dekker, Thorsten Ottosen
|
||||
// 05 May 2014 (Added move semantics) Andrzej Krzemienski
|
||||
//
|
||||
#ifndef BOOST_OPTIONAL_OPTIONAL_FLC_19NOV2002_HPP
|
||||
#define BOOST_OPTIONAL_OPTIONAL_FLC_19NOV2002_HPP
|
||||
@ -21,21 +23,35 @@
|
||||
|
||||
#include <boost/config.hpp>
|
||||
#include <boost/assert.hpp>
|
||||
#include <boost/static_assert.hpp>
|
||||
#include <boost/type.hpp>
|
||||
#include <boost/type_traits/alignment_of.hpp>
|
||||
#include <boost/type_traits/has_nothrow_constructor.hpp>
|
||||
#include <boost/type_traits/type_with_alignment.hpp>
|
||||
#include <boost/type_traits/remove_const.hpp>
|
||||
#include <boost/type_traits/remove_reference.hpp>
|
||||
#include <boost/type_traits/decay.hpp>
|
||||
#include <boost/type_traits/is_base_of.hpp>
|
||||
#include <boost/type_traits/is_lvalue_reference.hpp>
|
||||
#include <boost/type_traits/is_nothrow_move_assignable.hpp>
|
||||
#include <boost/type_traits/is_nothrow_move_constructible.hpp>
|
||||
#include <boost/type_traits/is_reference.hpp>
|
||||
#include <boost/type_traits/is_rvalue_reference.hpp>
|
||||
#include <boost/type_traits/is_same.hpp>
|
||||
#include <boost/mpl/if.hpp>
|
||||
#include <boost/mpl/bool.hpp>
|
||||
#include <boost/mpl/not.hpp>
|
||||
#include <boost/detail/reference_content.hpp>
|
||||
#include <boost/move/utility.hpp>
|
||||
#include <boost/none.hpp>
|
||||
#include <boost/utility/swap.hpp>
|
||||
#include <boost/utility/addressof.hpp>
|
||||
#include <boost/utility/compare_pointees.hpp>
|
||||
#include <boost/utility/enable_if.hpp>
|
||||
#include <boost/utility/explicit_operator_bool.hpp>
|
||||
#include <boost/utility/in_place_factory.hpp>
|
||||
#include <boost/utility/swap.hpp>
|
||||
|
||||
|
||||
|
||||
#include <boost/optional/optional_fwd.hpp>
|
||||
|
||||
@ -131,22 +147,41 @@ struct types_when_isnt_ref
|
||||
{
|
||||
typedef T const& reference_const_type ;
|
||||
typedef T & reference_type ;
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
typedef T && rval_reference_type ;
|
||||
static rval_reference_type move(reference_type r) { return boost::move(r); }
|
||||
#endif
|
||||
typedef T const* pointer_const_type ;
|
||||
typedef T * pointer_type ;
|
||||
typedef T const& argument_type ;
|
||||
} ;
|
||||
|
||||
template<class T>
|
||||
struct types_when_is_ref
|
||||
{
|
||||
typedef BOOST_DEDUCED_TYPENAME remove_reference<T>::type raw_type ;
|
||||
|
||||
typedef raw_type& reference_const_type ;
|
||||
typedef raw_type& reference_type ;
|
||||
typedef raw_type* pointer_const_type ;
|
||||
typedef raw_type* pointer_type ;
|
||||
typedef raw_type& argument_type ;
|
||||
typedef raw_type& reference_const_type ;
|
||||
typedef raw_type& reference_type ;
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
typedef BOOST_DEDUCED_TYPENAME remove_const<raw_type>::type&& rval_reference_type ;
|
||||
static reference_type move(reference_type r) { return r; }
|
||||
#endif
|
||||
typedef raw_type* pointer_const_type ;
|
||||
typedef raw_type* pointer_type ;
|
||||
typedef raw_type& argument_type ;
|
||||
} ;
|
||||
|
||||
template <class To, class From>
|
||||
void prevent_binding_rvalue_ref_to_optional_lvalue_ref()
|
||||
{
|
||||
#ifndef BOOST_OPTIONAL_ALLOW_BINDING_TO_RVALUES
|
||||
BOOST_STATIC_ASSERT_MSG(
|
||||
!boost::is_lvalue_reference<To>::value || !boost::is_rvalue_reference<From>::value,
|
||||
"binding rvalue references to optional lvalue references is disallowed");
|
||||
#endif
|
||||
}
|
||||
|
||||
struct optional_tag {} ;
|
||||
|
||||
template<class T>
|
||||
@ -180,10 +215,11 @@ class optional_base : public optional_tag
|
||||
typedef BOOST_DEDUCED_TYPENAME mpl::if_<is_reference_predicate,types_when_ref,types_when_not_ref>::type types ;
|
||||
|
||||
protected:
|
||||
typedef bool (this_type::*unspecified_bool_type)() const;
|
||||
|
||||
typedef BOOST_DEDUCED_TYPENAME types::reference_type reference_type ;
|
||||
typedef BOOST_DEDUCED_TYPENAME types::reference_const_type reference_const_type ;
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
typedef BOOST_DEDUCED_TYPENAME types::rval_reference_type rval_reference_type ;
|
||||
#endif
|
||||
typedef BOOST_DEDUCED_TYPENAME types::pointer_type pointer_type ;
|
||||
typedef BOOST_DEDUCED_TYPENAME types::pointer_const_type pointer_const_type ;
|
||||
typedef BOOST_DEDUCED_TYPENAME types::argument_type argument_type ;
|
||||
@ -209,6 +245,17 @@ class optional_base : public optional_tag
|
||||
construct(val);
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// move-construct an optional<T> initialized from an rvalue-ref to 'val'.
|
||||
// Can throw if T::T(T&&) does
|
||||
optional_base ( rval_reference_type val )
|
||||
:
|
||||
m_initialized(false)
|
||||
{
|
||||
construct( boost::move(val) );
|
||||
}
|
||||
#endif
|
||||
|
||||
// Creates an optional<T> initialized with 'val' IFF cond is true, otherwise creates an uninitialzed optional<T>.
|
||||
// Can throw if T::T(T const&) does
|
||||
optional_base ( bool cond, argument_type val )
|
||||
@ -229,7 +276,29 @@ class optional_base : public optional_tag
|
||||
construct(rhs.get_impl());
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Creates a deep move of another optional<T>
|
||||
// Can throw if T::T(T&&) does
|
||||
optional_base ( optional_base&& rhs )
|
||||
:
|
||||
m_initialized(false)
|
||||
{
|
||||
if ( rhs.is_initialized() )
|
||||
construct( boost::move(rhs.get_impl()) );
|
||||
}
|
||||
#endif
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
|
||||
template<class Expr, class PtrExpr>
|
||||
explicit optional_base ( Expr&& expr, PtrExpr const* tag )
|
||||
:
|
||||
m_initialized(false)
|
||||
{
|
||||
construct(boost::forward<Expr>(expr),tag);
|
||||
}
|
||||
|
||||
#else
|
||||
// This is used for both converting and in-place constructions.
|
||||
// Derived classes use the 'tag' to select the appropriate
|
||||
// implementation (the correct 'construct()' overload)
|
||||
@ -241,6 +310,7 @@ class optional_base : public optional_tag
|
||||
construct(expr,tag);
|
||||
}
|
||||
|
||||
#endif
|
||||
|
||||
|
||||
// No-throw (assuming T::~T() doesn't)
|
||||
@ -261,6 +331,24 @@ class optional_base : public optional_tag
|
||||
construct(rhs.get_impl());
|
||||
}
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Assigns from another optional<T> (deep-moves the rhs value)
|
||||
void assign ( optional_base&& rhs )
|
||||
{
|
||||
if (is_initialized())
|
||||
{
|
||||
if ( rhs.is_initialized() )
|
||||
assign_value(boost::move(rhs.get_impl()), is_reference_predicate() );
|
||||
else destroy();
|
||||
}
|
||||
else
|
||||
{
|
||||
if ( rhs.is_initialized() )
|
||||
construct(boost::move(rhs.get_impl()));
|
||||
}
|
||||
}
|
||||
#endif
|
||||
|
||||
// Assigns from another _convertible_ optional<U> (deep-copies the rhs value)
|
||||
template<class U>
|
||||
@ -279,6 +367,26 @@ class optional_base : public optional_tag
|
||||
}
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// move-assigns from another _convertible_ optional<U> (deep-moves from the rhs value)
|
||||
template<class U>
|
||||
void assign ( optional<U>&& rhs )
|
||||
{
|
||||
typedef BOOST_DEDUCED_TYPENAME optional<U>::rval_reference_type ref_type;
|
||||
if (is_initialized())
|
||||
{
|
||||
if ( rhs.is_initialized() )
|
||||
assign_value(static_cast<ref_type>(rhs.get()), is_reference_predicate() );
|
||||
else destroy();
|
||||
}
|
||||
else
|
||||
{
|
||||
if ( rhs.is_initialized() )
|
||||
construct(static_cast<ref_type>(rhs.get()));
|
||||
}
|
||||
}
|
||||
#endif
|
||||
|
||||
// Assigns from a T (deep-copies the rhs value)
|
||||
void assign ( argument_type val )
|
||||
{
|
||||
@ -286,26 +394,48 @@ class optional_base : public optional_tag
|
||||
assign_value(val, is_reference_predicate() );
|
||||
else construct(val);
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Assigns from a T (deep-moves the rhs value)
|
||||
void assign ( rval_reference_type val )
|
||||
{
|
||||
if (is_initialized())
|
||||
assign_value( boost::move(val), is_reference_predicate() );
|
||||
else construct( boost::move(val) );
|
||||
}
|
||||
#endif
|
||||
|
||||
// Assigns from "none", destroying the current value, if any, leaving this UNINITIALIZED
|
||||
// No-throw (assuming T::~T() doesn't)
|
||||
void assign ( none_t ) { destroy(); }
|
||||
void assign ( none_t ) BOOST_NOEXCEPT { destroy(); }
|
||||
|
||||
#ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
template<class Expr, class ExprPtr>
|
||||
void assign_expr ( Expr&& expr, ExprPtr const* tag )
|
||||
{
|
||||
if (is_initialized())
|
||||
assign_expr_to_initialized(boost::forward<Expr>(expr),tag);
|
||||
else construct(boost::forward<Expr>(expr),tag);
|
||||
}
|
||||
#else
|
||||
template<class Expr>
|
||||
void assign_expr ( Expr const& expr, Expr const* tag )
|
||||
{
|
||||
if (is_initialized())
|
||||
assign_expr_to_initialized(expr,tag);
|
||||
else construct(expr,tag);
|
||||
}
|
||||
{
|
||||
if (is_initialized())
|
||||
assign_expr_to_initialized(expr,tag);
|
||||
else construct(expr,tag);
|
||||
}
|
||||
#endif
|
||||
|
||||
#endif
|
||||
|
||||
public :
|
||||
|
||||
// Destroys the current value, if any, leaving this UNINITIALIZED
|
||||
// No-throw (assuming T::~T() doesn't)
|
||||
void reset() { destroy(); }
|
||||
void reset() BOOST_NOEXCEPT { destroy(); }
|
||||
|
||||
// Replaces the current value -if any- with 'val'
|
||||
void reset ( argument_type val ) { assign(val); }
|
||||
@ -325,8 +455,51 @@ class optional_base : public optional_tag
|
||||
new (m_storage.address()) internal_type(val) ;
|
||||
m_initialized = true ;
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
void construct ( rval_reference_type val )
|
||||
{
|
||||
new (m_storage.address()) internal_type( types::move(val) ) ;
|
||||
m_initialized = true ;
|
||||
}
|
||||
#endif
|
||||
|
||||
#ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Constructs in-place using the given factory
|
||||
template<class Expr>
|
||||
void construct ( Expr&& factory, in_place_factory_base const* )
|
||||
{
|
||||
BOOST_STATIC_ASSERT ( ::boost::mpl::not_<is_reference_predicate>::value ) ;
|
||||
boost_optional_detail::construct<value_type>(factory, m_storage.address());
|
||||
m_initialized = true ;
|
||||
}
|
||||
|
||||
// Constructs in-place using the given typed factory
|
||||
template<class Expr>
|
||||
void construct ( Expr&& factory, typed_in_place_factory_base const* )
|
||||
{
|
||||
BOOST_STATIC_ASSERT ( ::boost::mpl::not_<is_reference_predicate>::value ) ;
|
||||
factory.apply(m_storage.address()) ;
|
||||
m_initialized = true ;
|
||||
}
|
||||
|
||||
template<class Expr>
|
||||
void assign_expr_to_initialized ( Expr&& factory, in_place_factory_base const* tag )
|
||||
{
|
||||
destroy();
|
||||
construct(factory,tag);
|
||||
}
|
||||
|
||||
// Constructs in-place using the given typed factory
|
||||
template<class Expr>
|
||||
void assign_expr_to_initialized ( Expr&& factory, typed_in_place_factory_base const* tag )
|
||||
{
|
||||
destroy();
|
||||
construct(factory,tag);
|
||||
}
|
||||
#else
|
||||
// Constructs in-place using the given factory
|
||||
template<class Expr>
|
||||
void construct ( Expr const& factory, in_place_factory_base const* )
|
||||
@ -361,7 +534,31 @@ class optional_base : public optional_tag
|
||||
}
|
||||
#endif
|
||||
|
||||
// Constructs using any expression implicitely convertible to the single argument
|
||||
#endif
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Constructs using any expression implicitly convertible to the single argument
|
||||
// of a one-argument T constructor.
|
||||
// Converting constructions of optional<T> from optional<U> uses this function with
|
||||
// 'Expr' being of type 'U' and relying on a converting constructor of T from U.
|
||||
template<class Expr>
|
||||
void construct ( Expr&& expr, void const* )
|
||||
{
|
||||
new (m_storage.address()) internal_type(boost::forward<Expr>(expr)) ;
|
||||
m_initialized = true ;
|
||||
}
|
||||
|
||||
// Assigns using a form any expression implicitly convertible to the single argument
|
||||
// of a T's assignment operator.
|
||||
// Converting assignments of optional<T> from optional<U> uses this function with
|
||||
// 'Expr' being of type 'U' and relying on a converting assignment of T from U.
|
||||
template<class Expr>
|
||||
void assign_expr_to_initialized ( Expr&& expr, void const* )
|
||||
{
|
||||
assign_value(boost::forward<Expr>(expr), is_reference_predicate());
|
||||
}
|
||||
#else
|
||||
// Constructs using any expression implicitly convertible to the single argument
|
||||
// of a one-argument T constructor.
|
||||
// Converting constructions of optional<T> from optional<U> uses this function with
|
||||
// 'Expr' being of type 'U' and relying on a converting constructor of T from U.
|
||||
@ -372,7 +569,7 @@ class optional_base : public optional_tag
|
||||
m_initialized = true ;
|
||||
}
|
||||
|
||||
// Assigns using a form any expression implicitely convertible to the single argument
|
||||
// Assigns using a form any expression implicitly convertible to the single argument
|
||||
// of a T's assignment operator.
|
||||
// Converting assignments of optional<T> from optional<U> uses this function with
|
||||
// 'Expr' being of type 'U' and relying on a converting assignment of T from U.
|
||||
@ -382,6 +579,8 @@ class optional_base : public optional_tag
|
||||
assign_value(expr, is_reference_predicate());
|
||||
}
|
||||
|
||||
#endif
|
||||
|
||||
#ifdef BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION
|
||||
// BCB5.64 (and probably lower versions) workaround.
|
||||
// The in-place factories are supported by means of catch-all constructors
|
||||
@ -395,6 +594,20 @@ class optional_base : public optional_tag
|
||||
// For VC<=70 compilers this workaround dosen't work becasue the comnpiler issues and error
|
||||
// instead of choosing the wrong overload
|
||||
//
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Notice that 'Expr' will be optional<T> or optional<U> (but not optional_base<..>)
|
||||
template<class Expr>
|
||||
void construct ( Expr&& expr, optional_tag const* )
|
||||
{
|
||||
if ( expr.is_initialized() )
|
||||
{
|
||||
// An exception can be thrown here.
|
||||
// It it happens, THIS will be left uninitialized.
|
||||
new (m_storage.address()) internal_type(types::move(expr.get())) ;
|
||||
m_initialized = true ;
|
||||
}
|
||||
}
|
||||
#else
|
||||
// Notice that 'Expr' will be optional<T> or optional<U> (but not optional_base<..>)
|
||||
template<class Expr>
|
||||
void construct ( Expr const& expr, optional_tag const* )
|
||||
@ -408,9 +621,14 @@ class optional_base : public optional_tag
|
||||
}
|
||||
}
|
||||
#endif
|
||||
#endif // defined BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION
|
||||
|
||||
void assign_value ( argument_type val, is_not_reference_tag ) { get_impl() = val; }
|
||||
void assign_value ( argument_type val, is_reference_tag ) { construct(val); }
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
void assign_value ( rval_reference_type val, is_not_reference_tag ) { get_impl() = static_cast<rval_reference_type>(val); }
|
||||
void assign_value ( rval_reference_type val, is_reference_tag ) { construct( static_cast<rval_reference_type>(val) ); }
|
||||
#endif
|
||||
|
||||
void destroy()
|
||||
{
|
||||
@ -418,8 +636,6 @@ class optional_base : public optional_tag
|
||||
destroy_impl(is_reference_predicate()) ;
|
||||
}
|
||||
|
||||
unspecified_bool_type safe_bool() const { return m_initialized ? &this_type::is_initialized : 0 ; }
|
||||
|
||||
reference_const_type get_impl() const { return dereference(get_object(), is_reference_predicate() ) ; }
|
||||
reference_type get_impl() { return dereference(get_object(), is_reference_predicate() ) ; }
|
||||
|
||||
@ -479,8 +695,6 @@ class optional : public optional_detail::optional_base<T>
|
||||
{
|
||||
typedef optional_detail::optional_base<T> base ;
|
||||
|
||||
typedef BOOST_DEDUCED_TYPENAME base::unspecified_bool_type unspecified_bool_type ;
|
||||
|
||||
public :
|
||||
|
||||
typedef optional<T> this_type ;
|
||||
@ -488,22 +702,32 @@ class optional : public optional_detail::optional_base<T>
|
||||
typedef BOOST_DEDUCED_TYPENAME base::value_type value_type ;
|
||||
typedef BOOST_DEDUCED_TYPENAME base::reference_type reference_type ;
|
||||
typedef BOOST_DEDUCED_TYPENAME base::reference_const_type reference_const_type ;
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
typedef BOOST_DEDUCED_TYPENAME base::rval_reference_type rval_reference_type ;
|
||||
#endif
|
||||
typedef BOOST_DEDUCED_TYPENAME base::pointer_type pointer_type ;
|
||||
typedef BOOST_DEDUCED_TYPENAME base::pointer_const_type pointer_const_type ;
|
||||
typedef BOOST_DEDUCED_TYPENAME base::argument_type argument_type ;
|
||||
|
||||
// Creates an optional<T> uninitialized.
|
||||
// No-throw
|
||||
optional() : base() {}
|
||||
optional() BOOST_NOEXCEPT : base() {}
|
||||
|
||||
// Creates an optional<T> uninitialized.
|
||||
// No-throw
|
||||
optional( none_t none_ ) : base(none_) {}
|
||||
optional( none_t none_ ) BOOST_NOEXCEPT : base(none_) {}
|
||||
|
||||
// Creates an optional<T> initialized with 'val'.
|
||||
// Can throw if T::T(T const&) does
|
||||
optional ( argument_type val ) : base(val) {}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Creates an optional<T> initialized with 'move(val)'.
|
||||
// Can throw if T::T(T &&) does
|
||||
optional ( rval_reference_type val ) : base( boost::forward<T>(val) )
|
||||
{optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, rval_reference_type>();}
|
||||
#endif
|
||||
|
||||
// Creates an optional<T> initialized with 'val' IFF cond is true, otherwise creates an uninitialized optional.
|
||||
// Can throw if T::T(T const&) does
|
||||
optional ( bool cond, argument_type val ) : base(cond,val) {}
|
||||
@ -521,40 +745,94 @@ class optional : public optional_detail::optional_base<T>
|
||||
if ( rhs.is_initialized() )
|
||||
this->construct(rhs.get());
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Creates a deep move of another convertible optional<U>
|
||||
// Requires a valid conversion from U to T.
|
||||
// Can throw if T::T(U&&) does
|
||||
template<class U>
|
||||
explicit optional ( optional<U> && rhs )
|
||||
:
|
||||
base()
|
||||
{
|
||||
if ( rhs.is_initialized() )
|
||||
this->construct( boost::move(rhs.get()) );
|
||||
}
|
||||
#endif
|
||||
|
||||
#ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
|
||||
// Creates an optional<T> with an expression which can be either
|
||||
// (a) An instance of InPlaceFactory (i.e. in_place(a,b,...,n);
|
||||
// (b) An instance of TypedInPlaceFactory ( i.e. in_place<T>(a,b,...,n);
|
||||
// (c) Any expression implicitely convertible to the single type
|
||||
// (c) Any expression implicitly convertible to the single type
|
||||
// of a one-argument T's constructor.
|
||||
// (d*) Weak compilers (BCB) might also resolved Expr as optional<T> and optional<U>
|
||||
// even though explicit overloads are present for these.
|
||||
// Depending on the above some T ctor is called.
|
||||
// Can throw is the resolved T ctor throws.
|
||||
// Can throw if the resolved T ctor throws.
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
|
||||
|
||||
template<class Expr>
|
||||
explicit optional ( Expr&& expr,
|
||||
BOOST_DEDUCED_TYPENAME boost::disable_if_c<
|
||||
(boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type>::value) ||
|
||||
boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type, none_t>::value >::type* = 0
|
||||
)
|
||||
: base(boost::forward<Expr>(expr),boost::addressof(expr))
|
||||
{optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, Expr&&>();}
|
||||
|
||||
#else
|
||||
template<class Expr>
|
||||
explicit optional ( Expr const& expr ) : base(expr,boost::addressof(expr)) {}
|
||||
#endif
|
||||
#endif // !defined BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
#endif // !defined BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
|
||||
|
||||
// Creates a deep copy of another optional<T>
|
||||
// Can throw if T::T(T const&) does
|
||||
optional ( optional const& rhs ) : base( static_cast<base const&>(rhs) ) {}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Creates a deep move of another optional<T>
|
||||
// Can throw if T::T(T&&) does
|
||||
optional ( optional && rhs )
|
||||
BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value)
|
||||
: base( boost::move(rhs) )
|
||||
{}
|
||||
|
||||
#endif
|
||||
// No-throw (assuming T::~T() doesn't)
|
||||
~optional() {}
|
||||
|
||||
#if !defined(BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT) && !defined(BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION)
|
||||
// Assigns from an expression. See corresponding constructor.
|
||||
// Basic Guarantee: If the resolved T ctor throws, this is left UNINITIALIZED
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
|
||||
template<class Expr>
|
||||
BOOST_DEDUCED_TYPENAME boost::disable_if_c<
|
||||
boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type>::value ||
|
||||
boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type, none_t>::value,
|
||||
optional&
|
||||
>::type
|
||||
operator= ( Expr&& expr )
|
||||
{
|
||||
optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, Expr&&>();
|
||||
this->assign_expr(boost::forward<Expr>(expr),boost::addressof(expr));
|
||||
return *this ;
|
||||
}
|
||||
|
||||
#else
|
||||
template<class Expr>
|
||||
optional& operator= ( Expr const& expr )
|
||||
{
|
||||
this->assign_expr(expr,boost::addressof(expr));
|
||||
return *this ;
|
||||
}
|
||||
#endif
|
||||
#endif // !defined BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
#endif // !defined(BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT) && !defined(BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION)
|
||||
|
||||
// Assigns from another convertible optional<U> (converts && deep-copies the rhs value)
|
||||
// Copy-assigns from another convertible optional<U> (converts && deep-copies the rhs value)
|
||||
// Requires a valid conversion from U to T.
|
||||
// Basic Guarantee: If T::T( U const& ) throws, this is left UNINITIALIZED
|
||||
template<class U>
|
||||
@ -563,6 +841,18 @@ class optional : public optional_detail::optional_base<T>
|
||||
this->assign(rhs);
|
||||
return *this ;
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Move-assigns from another convertible optional<U> (converts && deep-moves the rhs value)
|
||||
// Requires a valid conversion from U to T.
|
||||
// Basic Guarantee: If T::T( U && ) throws, this is left UNINITIALIZED
|
||||
template<class U>
|
||||
optional& operator= ( optional<U> && rhs )
|
||||
{
|
||||
this->assign(boost::move(rhs));
|
||||
return *this ;
|
||||
}
|
||||
#endif
|
||||
|
||||
// Assigns from another optional<T> (deep-copies the rhs value)
|
||||
// Basic Guarantee: If T::T( T const& ) throws, this is left UNINITIALIZED
|
||||
@ -573,6 +863,16 @@ class optional : public optional_detail::optional_base<T>
|
||||
return *this ;
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Assigns from another optional<T> (deep-moves the rhs value)
|
||||
optional& operator= ( optional && rhs )
|
||||
BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && ::boost::is_nothrow_move_assignable<T>::value)
|
||||
{
|
||||
this->assign( static_cast<base &&>(rhs) ) ;
|
||||
return *this ;
|
||||
}
|
||||
#endif
|
||||
|
||||
// Assigns from a T (deep-copies the rhs value)
|
||||
// Basic Guarantee: If T::( T const& ) throws, this is left UNINITIALIZED
|
||||
optional& operator= ( argument_type val )
|
||||
@ -581,20 +881,30 @@ class optional : public optional_detail::optional_base<T>
|
||||
return *this ;
|
||||
}
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
// Assigns from a T (deep-moves the rhs value)
|
||||
optional& operator= ( rval_reference_type val )
|
||||
{
|
||||
optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, rval_reference_type>();
|
||||
this->assign( boost::move(val) ) ;
|
||||
return *this ;
|
||||
}
|
||||
#endif
|
||||
|
||||
// Assigns from a "none"
|
||||
// Which destroys the current value, if any, leaving this UNINITIALIZED
|
||||
// No-throw (assuming T::~T() doesn't)
|
||||
optional& operator= ( none_t none_ )
|
||||
optional& operator= ( none_t none_ ) BOOST_NOEXCEPT
|
||||
{
|
||||
this->assign( none_ ) ;
|
||||
return *this ;
|
||||
}
|
||||
|
||||
void swap( optional & arg )
|
||||
BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && ::boost::is_nothrow_move_assignable<T>::value)
|
||||
{
|
||||
// allow for Koenig lookup
|
||||
using boost::swap;
|
||||
swap(*this, arg);
|
||||
boost::swap(*this, arg);
|
||||
}
|
||||
|
||||
|
||||
@ -620,15 +930,19 @@ class optional : public optional_detail::optional_base<T>
|
||||
reference_const_type operator *() const { return this->get() ; }
|
||||
reference_type operator *() { return this->get() ; }
|
||||
|
||||
// implicit conversion to "bool"
|
||||
// No-throw
|
||||
operator unspecified_bool_type() const { return this->safe_bool() ; }
|
||||
|
||||
// This is provided for those compilers which don't like the conversion to bool
|
||||
// on some contexts.
|
||||
bool operator!() const { return !this->is_initialized() ; }
|
||||
bool operator!() const BOOST_NOEXCEPT { return !this->is_initialized() ; }
|
||||
|
||||
BOOST_EXPLICIT_OPERATOR_BOOL()
|
||||
} ;
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
template<class T>
|
||||
class optional<T&&>
|
||||
{
|
||||
BOOST_STATIC_ASSERT_MSG(sizeof(T) == 0, "Optional rvalue references are illegal.");
|
||||
} ;
|
||||
#endif
|
||||
|
||||
// Returns optional<T>(v)
|
||||
template<class T>
|
||||
inline
|
||||
@ -835,8 +1149,8 @@ bool operator >= ( T const& x, optional<T> const& y )
|
||||
|
||||
template<class T>
|
||||
inline
|
||||
bool operator == ( optional<T> const& x, none_t )
|
||||
{ return equal_pointees(x, optional<T>() ); }
|
||||
bool operator == ( optional<T> const& x, none_t ) BOOST_NOEXCEPT
|
||||
{ return !x; }
|
||||
|
||||
template<class T>
|
||||
inline
|
||||
@ -845,8 +1159,8 @@ bool operator < ( optional<T> const& x, none_t )
|
||||
|
||||
template<class T>
|
||||
inline
|
||||
bool operator != ( optional<T> const& x, none_t y )
|
||||
{ return !( x == y ) ; }
|
||||
bool operator != ( optional<T> const& x, none_t ) BOOST_NOEXCEPT
|
||||
{ return bool(x); }
|
||||
|
||||
template<class T>
|
||||
inline
|
||||
@ -869,8 +1183,8 @@ bool operator >= ( optional<T> const& x, none_t y )
|
||||
|
||||
template<class T>
|
||||
inline
|
||||
bool operator == ( none_t , optional<T> const& y )
|
||||
{ return equal_pointees(optional<T>() ,y); }
|
||||
bool operator == ( none_t , optional<T> const& y ) BOOST_NOEXCEPT
|
||||
{ return !y; }
|
||||
|
||||
template<class T>
|
||||
inline
|
||||
@ -879,8 +1193,8 @@ bool operator < ( none_t , optional<T> const& y )
|
||||
|
||||
template<class T>
|
||||
inline
|
||||
bool operator != ( none_t x, optional<T> const& y )
|
||||
{ return !( x == y ) ; }
|
||||
bool operator != ( none_t, optional<T> const& y ) BOOST_NOEXCEPT
|
||||
{ return bool(y); }
|
||||
|
||||
template<class T>
|
||||
inline
|
||||
@ -928,6 +1242,37 @@ struct swap_selector<true>
|
||||
}
|
||||
};
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
template<>
|
||||
struct swap_selector<false>
|
||||
{
|
||||
template<class T>
|
||||
static void optional_swap ( optional<T>& x, optional<T>& y )
|
||||
//BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::swap(*x, *y)))
|
||||
{
|
||||
if(x)
|
||||
{
|
||||
if (y)
|
||||
{
|
||||
boost::swap(*x, *y);
|
||||
}
|
||||
else
|
||||
{
|
||||
y = boost::move(*x);
|
||||
x = boost::none;
|
||||
}
|
||||
}
|
||||
else
|
||||
{
|
||||
if (y)
|
||||
{
|
||||
x = boost::move(*y);
|
||||
y = boost::none;
|
||||
}
|
||||
}
|
||||
}
|
||||
};
|
||||
#else
|
||||
template<>
|
||||
struct swap_selector<false>
|
||||
{
|
||||
@ -954,6 +1299,7 @@ struct swap_selector<false>
|
||||
}
|
||||
}
|
||||
};
|
||||
#endif // !defined BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
|
||||
} // namespace optional_detail
|
||||
|
||||
@ -961,6 +1307,7 @@ template<class T>
|
||||
struct optional_swap_should_use_default_constructor : has_nothrow_default_constructor<T> {} ;
|
||||
|
||||
template<class T> inline void swap ( optional<T>& x, optional<T>& y )
|
||||
//BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::swap(*x, *y)))
|
||||
{
|
||||
optional_detail::swap_selector<optional_swap_should_use_default_constructor<T>::value>::optional_swap(x, y);
|
||||
}
|
||||
|
||||
@ -11,15 +11,18 @@
|
||||
//
|
||||
// Revisions:
|
||||
// 10 May 2008 (added swap related forward declaration) Niels Dekker
|
||||
//
|
||||
// 17 Apr 2014 (added noexcept) Andrzej Krzemienski
|
||||
//
|
||||
#ifndef BOOST_OPTIONAL_OPTIONAL_FWD_FLC_19NOV2002_HPP
|
||||
#define BOOST_OPTIONAL_OPTIONAL_FWD_FLC_19NOV2002_HPP
|
||||
#include <boost/config.hpp>
|
||||
|
||||
|
||||
namespace boost {
|
||||
|
||||
template<class T> class optional ;
|
||||
|
||||
template<class T> void swap ( optional<T>& , optional<T>& ) ;
|
||||
template<class T> void swap ( optional<T>& , optional<T>& );
|
||||
|
||||
template<class T> struct optional_swap_should_use_default_constructor ;
|
||||
|
||||
|
||||
@ -21,6 +21,8 @@ import testing ;
|
||||
[ run optional_test_ref.cpp ]
|
||||
[ run optional_test_inplace.cpp ]
|
||||
[ run optional_test_io.cpp ]
|
||||
[ run optional_test_move.cpp ]
|
||||
[ run optional_test_equals_none.cpp ]
|
||||
[ compile-fail optional_test_fail1.cpp ]
|
||||
[ compile-fail optional_test_fail3a.cpp ]
|
||||
[ compile-fail optional_test_fail3b.cpp ]
|
||||
@ -29,5 +31,12 @@ import testing ;
|
||||
[ compile-fail optional_test_ref_fail4.cpp ]
|
||||
[ compile-fail optional_test_inplace_fail.cpp ]
|
||||
[ compile-fail optional_test_inplace_fail2.cpp ]
|
||||
[ compile-fail optional_test_fail_implicit_bool_convert.cpp ]
|
||||
[ compile-fail optional_test_fail_copying_a_moveable_type.cpp ]
|
||||
[ compile-fail optional_test_fail_optional_rvalue_ref.cpp ]
|
||||
[ compile-fail optional_test_ref_fail_init_from_Trefref.cpp ]
|
||||
[ compile-fail optional_test_ref_fail_init_from_Urefref.cpp ]
|
||||
[ compile-fail optional_test_ref_fail_assign_from_Trefref.cpp ]
|
||||
[ compile-fail optional_test_ref_fail_assign_from_Urefref.cpp ]
|
||||
;
|
||||
}
|
||||
|
||||
@ -1086,8 +1086,8 @@ namespace optional_swap_test
|
||||
//
|
||||
void swap(boost::optional<class_whose_explicit_ctor_should_be_used> & x, boost::optional<class_whose_explicit_ctor_should_be_used> & y)
|
||||
{
|
||||
bool hasX = x;
|
||||
bool hasY = y;
|
||||
bool hasX(x);
|
||||
bool hasY(y);
|
||||
|
||||
if ( !hasX && !hasY )
|
||||
return;
|
||||
|
||||
68
test/optional_test_equals_none.cpp
Normal file
68
test/optional_test_equals_none.cpp
Normal file
@ -0,0 +1,68 @@
|
||||
// Copyright (C) 2014 Andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
// Revisions:
|
||||
//
|
||||
#include<iostream>
|
||||
#include<stdexcept>
|
||||
#include<string>
|
||||
|
||||
#define BOOST_ENABLE_ASSERT_HANDLER
|
||||
|
||||
#include "boost/bind/apply.hpp" // Included just to test proper interaction with boost::apply<> as reported by Daniel Wallin
|
||||
#include "boost/mpl/bool.hpp"
|
||||
#include "boost/mpl/bool_fwd.hpp" // For mpl::true_ and mpl::false_
|
||||
|
||||
#include "boost/optional/optional.hpp"
|
||||
|
||||
#ifdef __BORLANDC__
|
||||
#pragma hdrstop
|
||||
#endif
|
||||
|
||||
#include "boost/none.hpp"
|
||||
|
||||
#include "boost/test/minimal.hpp"
|
||||
|
||||
#include "optional_test_common.cpp"
|
||||
|
||||
struct SemiRegular // no operator==
|
||||
{
|
||||
private: void operator==(SemiRegular const&) const {}
|
||||
private: void operator!=(SemiRegular const&) const {}
|
||||
};
|
||||
|
||||
void test_equal_to_none_of_noncomparable_T()
|
||||
{
|
||||
optional<SemiRegular> i = SemiRegular();
|
||||
optional<SemiRegular> o;
|
||||
|
||||
BOOST_CHECK(i != boost::none);
|
||||
BOOST_CHECK(boost::none != i);
|
||||
BOOST_CHECK(o == boost::none);
|
||||
BOOST_CHECK(boost::none == o);
|
||||
}
|
||||
|
||||
int test_main( int, char* [] )
|
||||
{
|
||||
try
|
||||
{
|
||||
test_equal_to_none_of_noncomparable_T();
|
||||
|
||||
}
|
||||
catch ( ... )
|
||||
{
|
||||
BOOST_ERROR("Unexpected Exception caught!");
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
||||
36
test/optional_test_fail_copying_a_moveable_type.cpp
Normal file
36
test/optional_test_fail_copying_a_moveable_type.cpp
Normal file
@ -0,0 +1,36 @@
|
||||
// Copyright (C) 2014, Andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
#include "boost/optional.hpp"
|
||||
|
||||
class MoveOnly
|
||||
{
|
||||
public:
|
||||
int val;
|
||||
MoveOnly(int v) : val(v) {}
|
||||
MoveOnly(MoveOnly&& rhs) : val(rhs.val) { rhs.val = 0; }
|
||||
void operator=(MoveOnly&& rhs) {val = rhs.val; rhs.val = 0; }
|
||||
|
||||
private:
|
||||
MoveOnly(MoveOnly const&);
|
||||
void operator=(MoveOnly const&);
|
||||
};
|
||||
|
||||
//
|
||||
// THIS TEST SHOULD FAIL TO COMPILE
|
||||
//
|
||||
void test_copying_optional_with_noncopyable_T()
|
||||
{
|
||||
boost::optional<MoveOnly> opt1 ;
|
||||
boost::optional<MoveOnly> opt2(opt1) ;
|
||||
}
|
||||
|
||||
|
||||
28
test/optional_test_fail_implicit_bool_convert.cpp
Normal file
28
test/optional_test_fail_implicit_bool_convert.cpp
Normal file
@ -0,0 +1,28 @@
|
||||
// Copyright (C) 2014, Andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
#include "boost/optional.hpp"
|
||||
|
||||
//
|
||||
// THIS TEST SHOULD FAIL TO COMPILE
|
||||
//
|
||||
|
||||
#if !defined(BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS)
|
||||
|
||||
bool test_implicit_conversion_to_bool()
|
||||
{
|
||||
boost::optional<int> opt;
|
||||
return opt;
|
||||
}
|
||||
|
||||
#else
|
||||
# error "Test skipped: this compiler does not support explicit conversion operators."
|
||||
#endif
|
||||
19
test/optional_test_fail_optional_rvalue_ref.cpp
Normal file
19
test/optional_test_fail_optional_rvalue_ref.cpp
Normal file
@ -0,0 +1,19 @@
|
||||
// Copyright (C) 2014, Andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
#include "boost/optional.hpp"
|
||||
//
|
||||
// THIS TEST SHOULD FAIL TO COMPILE
|
||||
//
|
||||
|
||||
boost::optional<int&&> oi;
|
||||
|
||||
|
||||
414
test/optional_test_move.cpp
Normal file
414
test/optional_test_move.cpp
Normal file
@ -0,0 +1,414 @@
|
||||
// Copyright (C) 2014 Andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
// Revisions:
|
||||
//
|
||||
#include<iostream>
|
||||
#include<stdexcept>
|
||||
#include<string>
|
||||
|
||||
#define BOOST_ENABLE_ASSERT_HANDLER
|
||||
|
||||
#include "boost/bind/apply.hpp" // Included just to test proper interaction with boost::apply<> as reported by Daniel Wallin
|
||||
#include "boost/mpl/bool.hpp"
|
||||
#include "boost/mpl/bool_fwd.hpp" // For mpl::true_ and mpl::false_
|
||||
#include "boost/static_assert.hpp"
|
||||
|
||||
#include "boost/optional/optional.hpp"
|
||||
|
||||
#ifdef __BORLANDC__
|
||||
#pragma hdrstop
|
||||
#endif
|
||||
|
||||
#include "boost/none.hpp"
|
||||
|
||||
#include "boost/test/minimal.hpp"
|
||||
|
||||
#include "optional_test_common.cpp"
|
||||
|
||||
//#ifndef BOOST_OPTIONAL_NO_CONVERTING_ASSIGNMENT
|
||||
//#ifndef BOOST_OPTIONAL_NO_CONVERTING_COPY_CTOR
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
|
||||
enum State
|
||||
{
|
||||
sDefaultConstructed,
|
||||
sValueCopyConstructed,
|
||||
sValueMoveConstructed,
|
||||
sCopyConstructed,
|
||||
sMoveConstructed,
|
||||
sMoveAssigned,
|
||||
sCopyAssigned,
|
||||
sValueCopyAssigned,
|
||||
sValueMoveAssigned,
|
||||
sMovedFrom,
|
||||
sIntConstructed
|
||||
};
|
||||
|
||||
struct OracleVal
|
||||
{
|
||||
State s;
|
||||
int i;
|
||||
OracleVal(int i = 0) : s(sIntConstructed), i(i) {}
|
||||
};
|
||||
|
||||
|
||||
struct Oracle
|
||||
{
|
||||
State s;
|
||||
OracleVal val;
|
||||
|
||||
Oracle() : s(sDefaultConstructed) {}
|
||||
Oracle(const OracleVal& v) : s(sValueCopyConstructed), val(v) {}
|
||||
Oracle(OracleVal&& v) : s(sValueMoveConstructed), val(std::move(v)) {v.s = sMovedFrom;}
|
||||
Oracle(const Oracle& o) : s(sCopyConstructed), val(o.val) {}
|
||||
Oracle(Oracle&& o) : s(sMoveConstructed), val(std::move(o.val)) {o.s = sMovedFrom;}
|
||||
|
||||
Oracle& operator=(const OracleVal& v) { s = sValueCopyAssigned; val = v; return *this; }
|
||||
Oracle& operator=(OracleVal&& v) { s = sValueMoveAssigned; val = std::move(v); v.s = sMovedFrom; return *this; }
|
||||
Oracle& operator=(const Oracle& o) { s = sCopyAssigned; val = o.val; return *this; }
|
||||
Oracle& operator=(Oracle&& o) { s = sMoveAssigned; val = std::move(o.val); o.s = sMovedFrom; return *this; }
|
||||
};
|
||||
|
||||
bool operator==( Oracle const& a, Oracle const& b ) { return a.val.i == b.val.i; }
|
||||
bool operator!=( Oracle const& a, Oracle const& b ) { return a.val.i != b.val.i; }
|
||||
|
||||
|
||||
void test_move_ctor_from_U()
|
||||
{
|
||||
optional<Oracle> o1 ((OracleVal()));
|
||||
BOOST_CHECK(o1);
|
||||
BOOST_CHECK(o1->s == sValueMoveConstructed || o1->s == sMoveConstructed);
|
||||
|
||||
OracleVal v1;
|
||||
optional<Oracle> o2 (v1);
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->s == sValueCopyConstructed || o2->s == sCopyConstructed || o2->s == sMoveConstructed );
|
||||
BOOST_CHECK(v1.s == sIntConstructed);
|
||||
|
||||
optional<Oracle> o3 (boost::move(v1));
|
||||
BOOST_CHECK(o3);
|
||||
BOOST_CHECK(o3->s == sValueMoveConstructed || o3->s == sMoveConstructed);
|
||||
BOOST_CHECK(v1.s == sMovedFrom);
|
||||
}
|
||||
|
||||
void test_move_ctor_form_T()
|
||||
{
|
||||
optional<Oracle> o1 ((Oracle()));
|
||||
BOOST_CHECK(o1);
|
||||
BOOST_CHECK(o1->s == sMoveConstructed);
|
||||
|
||||
Oracle v1;
|
||||
optional<Oracle> o2 (v1);
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->s == sCopyConstructed);
|
||||
BOOST_CHECK(v1.s == sDefaultConstructed);
|
||||
|
||||
optional<Oracle> o3 (boost::move(v1));
|
||||
BOOST_CHECK(o3);
|
||||
BOOST_CHECK(o3->s == sMoveConstructed);
|
||||
BOOST_CHECK(v1.s == sMovedFrom);
|
||||
}
|
||||
|
||||
void test_move_ctor_from_optional_T()
|
||||
{
|
||||
optional<Oracle> o1;
|
||||
optional<Oracle> o2(boost::move(o1));
|
||||
|
||||
BOOST_CHECK(!o1);
|
||||
BOOST_CHECK(!o2);
|
||||
|
||||
optional<Oracle> o3((Oracle()));
|
||||
optional<Oracle> o4(boost::move(o3));
|
||||
BOOST_CHECK(o3);
|
||||
BOOST_CHECK(o4);
|
||||
BOOST_CHECK(o3->s == sMovedFrom);
|
||||
BOOST_CHECK(o4->s == sMoveConstructed);
|
||||
|
||||
optional<Oracle> o5((optional<Oracle>()));
|
||||
BOOST_CHECK(!o5);
|
||||
|
||||
optional<Oracle> o6((optional<Oracle>(Oracle())));
|
||||
BOOST_CHECK(o6);
|
||||
BOOST_CHECK(o6->s == sMoveConstructed);
|
||||
|
||||
optional<Oracle> o7(o6); // does copy ctor from non-const lvalue compile?
|
||||
}
|
||||
|
||||
void test_move_assign_from_U()
|
||||
{
|
||||
optional<Oracle> o1 = boost::none; // test if additional ctors didn't break it
|
||||
o1 = boost::none; // test if additional assignments didn't break it
|
||||
o1 = OracleVal();
|
||||
BOOST_CHECK(o1);
|
||||
|
||||
BOOST_CHECK(o1->s == sValueMoveConstructed);
|
||||
|
||||
o1 = OracleVal();
|
||||
BOOST_CHECK(o1);
|
||||
BOOST_CHECK(o1->s == sMoveAssigned);
|
||||
|
||||
OracleVal v1;
|
||||
optional<Oracle> o2;
|
||||
o2 = v1;
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->s == sValueCopyConstructed);
|
||||
BOOST_CHECK(v1.s == sIntConstructed);
|
||||
o2 = v1;
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->s == sCopyAssigned || o2->s == sMoveAssigned);
|
||||
BOOST_CHECK(v1.s == sIntConstructed);
|
||||
|
||||
optional<Oracle> o3;
|
||||
o3 = boost::move(v1);
|
||||
BOOST_CHECK(o3);
|
||||
BOOST_CHECK(o3->s == sValueMoveConstructed);
|
||||
BOOST_CHECK(v1.s == sMovedFrom);
|
||||
}
|
||||
|
||||
void test_move_assign_from_T()
|
||||
{
|
||||
optional<Oracle> o1;
|
||||
o1 = Oracle();
|
||||
BOOST_CHECK(o1);
|
||||
BOOST_CHECK(o1->s == sMoveConstructed);
|
||||
|
||||
o1 = Oracle();
|
||||
BOOST_CHECK(o1);
|
||||
BOOST_CHECK(o1->s == sMoveAssigned);
|
||||
|
||||
Oracle v1;
|
||||
optional<Oracle> o2;
|
||||
o2 = v1;
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->s == sCopyConstructed);
|
||||
BOOST_CHECK(v1.s == sDefaultConstructed);
|
||||
o2 = v1;
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->s == sCopyAssigned);
|
||||
BOOST_CHECK(v1.s == sDefaultConstructed);
|
||||
|
||||
optional<Oracle> o3;
|
||||
o3 = boost::move(v1);
|
||||
BOOST_CHECK(o3);
|
||||
BOOST_CHECK(o3->s == sMoveConstructed);
|
||||
BOOST_CHECK(v1.s == sMovedFrom);
|
||||
}
|
||||
|
||||
void test_move_assign_from_optional_T()
|
||||
{
|
||||
optional<Oracle> o1;
|
||||
optional<Oracle> o2;
|
||||
o1 = optional<Oracle>();
|
||||
BOOST_CHECK(!o1);
|
||||
optional<Oracle> o3((Oracle()));
|
||||
o1 = o3;
|
||||
BOOST_CHECK(o3);
|
||||
BOOST_CHECK(o3->s == sMoveConstructed);
|
||||
BOOST_CHECK(o1);
|
||||
BOOST_CHECK(o1->s == sCopyConstructed);
|
||||
|
||||
o2 = boost::move(o3);
|
||||
BOOST_CHECK(o3);
|
||||
BOOST_CHECK(o3->s == sMovedFrom);
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->s == sMoveConstructed);
|
||||
|
||||
o2 = optional<Oracle>((Oracle()));
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->s == sMoveAssigned);
|
||||
}
|
||||
|
||||
class MoveOnly
|
||||
{
|
||||
public:
|
||||
int val;
|
||||
MoveOnly(int v) : val(v) {}
|
||||
MoveOnly(MoveOnly&& rhs) : val(rhs.val) { rhs.val = 0; }
|
||||
void operator=(MoveOnly&& rhs) {val = rhs.val; rhs.val = 0; }
|
||||
|
||||
private:
|
||||
MoveOnly(MoveOnly const&);
|
||||
void operator=(MoveOnly const&);
|
||||
|
||||
friend class MoveOnlyB;
|
||||
};
|
||||
|
||||
void test_with_move_only()
|
||||
{
|
||||
optional<MoveOnly> o1;
|
||||
optional<MoveOnly> o2((MoveOnly(1)));
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->val == 1);
|
||||
optional<MoveOnly> o3 (boost::move(o1));
|
||||
BOOST_CHECK(!o3);
|
||||
optional<MoveOnly> o4 (boost::move(o2));
|
||||
BOOST_CHECK(o4);
|
||||
BOOST_CHECK(o4->val == 1);
|
||||
BOOST_CHECK(o2);
|
||||
BOOST_CHECK(o2->val == 0);
|
||||
|
||||
o3 = boost::move(o4);
|
||||
BOOST_CHECK(o3);
|
||||
BOOST_CHECK(o3->val == 1);
|
||||
BOOST_CHECK(o4);
|
||||
BOOST_CHECK(o4->val == 0);
|
||||
}
|
||||
|
||||
class MoveOnlyB
|
||||
{
|
||||
public:
|
||||
int val;
|
||||
MoveOnlyB(int v) : val(v) {}
|
||||
MoveOnlyB(MoveOnlyB&& rhs) : val(rhs.val) { rhs.val = 0; }
|
||||
void operator=(MoveOnlyB&& rhs) {val = rhs.val; rhs.val = 0; }
|
||||
MoveOnlyB(MoveOnly&& rhs) : val(rhs.val) { rhs.val = 0; }
|
||||
void operator=(MoveOnly&& rhs) {val = rhs.val; rhs.val = 0; }
|
||||
|
||||
private:
|
||||
MoveOnlyB(MoveOnlyB const&);
|
||||
void operator=(MoveOnlyB const&);
|
||||
MoveOnlyB(MoveOnly const&);
|
||||
void operator=(MoveOnly const&);
|
||||
};
|
||||
|
||||
void test_move_assign_from_optional_U()
|
||||
{
|
||||
optional<MoveOnly> a((MoveOnly(2)));
|
||||
optional<MoveOnlyB> b1;
|
||||
b1 = boost::move(a);
|
||||
|
||||
BOOST_CHECK(b1);
|
||||
BOOST_CHECK(b1->val == 2);
|
||||
BOOST_CHECK(a);
|
||||
BOOST_CHECK(a->val == 0);
|
||||
|
||||
b1 = MoveOnly(4);
|
||||
|
||||
BOOST_CHECK(b1);
|
||||
BOOST_CHECK(b1->val == 4);
|
||||
}
|
||||
|
||||
void test_move_ctor_from_optional_U()
|
||||
{
|
||||
optional<MoveOnly> a((MoveOnly(2)));
|
||||
optional<MoveOnlyB> b1(boost::move(a));
|
||||
|
||||
BOOST_CHECK(b1);
|
||||
BOOST_CHECK(b1->val == 2);
|
||||
BOOST_CHECK(a);
|
||||
BOOST_CHECK(a->val == 0);
|
||||
|
||||
optional<MoveOnlyB> b2(( optional<MoveOnly>(( MoveOnly(4) )) ));
|
||||
|
||||
BOOST_CHECK(b2);
|
||||
BOOST_CHECK(b2->val == 4);
|
||||
}
|
||||
|
||||
void test_swap()
|
||||
{
|
||||
optional<MoveOnly> a((MoveOnly(2)));
|
||||
optional<MoveOnly> b((MoveOnly(3)));
|
||||
swap(a, b);
|
||||
|
||||
BOOST_CHECK(a->val == 3);
|
||||
BOOST_CHECK(b->val == 2);
|
||||
}
|
||||
|
||||
void test_optional_ref_to_movables()
|
||||
{
|
||||
MoveOnly m(3);
|
||||
optional<MoveOnly&> orm = m;
|
||||
orm->val = 2;
|
||||
BOOST_CHECK(m.val == 2);
|
||||
|
||||
optional<MoveOnly&> orm2 = orm;
|
||||
orm2->val = 1;
|
||||
BOOST_CHECK(m.val == 1);
|
||||
BOOST_CHECK(orm->val == 1);
|
||||
|
||||
optional<MoveOnly&> orm3 = boost::move(orm);
|
||||
orm3->val = 4;
|
||||
BOOST_CHECK(m.val == 4);
|
||||
BOOST_CHECK(orm->val == 4);
|
||||
BOOST_CHECK(orm2->val == 4);
|
||||
}
|
||||
|
||||
// these 4 classes have different noexcept signatures in move operations
|
||||
struct NothrowBoth {
|
||||
NothrowBoth(NothrowBoth&&) BOOST_NOEXCEPT_IF(true) {};
|
||||
void operator=(NothrowBoth&&) BOOST_NOEXCEPT_IF(true) {};
|
||||
};
|
||||
struct NothrowCtor {
|
||||
NothrowCtor(NothrowCtor&&) BOOST_NOEXCEPT_IF(true) {};
|
||||
void operator=(NothrowCtor&&) BOOST_NOEXCEPT_IF(false) {};
|
||||
};
|
||||
struct NothrowAssign {
|
||||
NothrowAssign(NothrowAssign&&) BOOST_NOEXCEPT_IF(false) {};
|
||||
void operator=(NothrowAssign&&) BOOST_NOEXCEPT_IF(true) {};
|
||||
};
|
||||
struct NothrowNone {
|
||||
NothrowNone(NothrowNone&&) BOOST_NOEXCEPT_IF(false) {};
|
||||
void operator=(NothrowNone&&) BOOST_NOEXCEPT_IF(false) {};
|
||||
};
|
||||
|
||||
#ifndef BOOST_NO_NOEXCEPT
|
||||
|
||||
void test_noexcept() // this is a compile-time test
|
||||
{
|
||||
BOOST_STATIC_ASSERT(::boost::is_nothrow_move_constructible<optional<NothrowBoth> >::value);
|
||||
BOOST_STATIC_ASSERT(::boost::is_nothrow_move_assignable<optional<NothrowBoth> >::value);
|
||||
BOOST_STATIC_ASSERT(BOOST_NOEXCEPT_EXPR(optional<NothrowBoth>()));
|
||||
|
||||
BOOST_STATIC_ASSERT(::boost::is_nothrow_move_constructible<optional<NothrowCtor> >::value);
|
||||
BOOST_STATIC_ASSERT(!::boost::is_nothrow_move_assignable<optional<NothrowCtor> >::value);
|
||||
BOOST_STATIC_ASSERT(BOOST_NOEXCEPT_EXPR(optional<NothrowCtor>()));
|
||||
|
||||
BOOST_STATIC_ASSERT(!::boost::is_nothrow_move_constructible<optional<NothrowAssign> >::value);
|
||||
BOOST_STATIC_ASSERT(!::boost::is_nothrow_move_assignable<optional<NothrowAssign> >::value);
|
||||
BOOST_STATIC_ASSERT(BOOST_NOEXCEPT_EXPR(optional<NothrowAssign>()));
|
||||
|
||||
BOOST_STATIC_ASSERT(!::boost::is_nothrow_move_constructible<optional<NothrowNone> >::value);
|
||||
BOOST_STATIC_ASSERT(!::boost::is_nothrow_move_assignable<optional<NothrowNone> >::value);
|
||||
BOOST_STATIC_ASSERT(BOOST_NOEXCEPT_EXPR(optional<NothrowNone>()));
|
||||
}
|
||||
#endif // !defned BOOST_NO_NOEXCEPT
|
||||
|
||||
#endif
|
||||
|
||||
int test_main( int, char* [] )
|
||||
{
|
||||
try
|
||||
{
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
test_move_ctor_from_U();
|
||||
test_move_ctor_form_T();
|
||||
test_move_ctor_from_optional_T();
|
||||
test_move_ctor_from_optional_U();
|
||||
test_move_assign_from_U();
|
||||
test_move_assign_from_T();
|
||||
test_move_assign_from_optional_T();
|
||||
test_move_assign_from_optional_U();
|
||||
test_with_move_only();
|
||||
test_optional_ref_to_movables();
|
||||
test_swap();
|
||||
#endif
|
||||
}
|
||||
catch ( ... )
|
||||
{
|
||||
BOOST_ERROR("Unexpected Exception caught!");
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
||||
26
test/optional_test_ref_fail_assign_from_Trefref.cpp
Normal file
26
test/optional_test_ref_fail_assign_from_Trefref.cpp
Normal file
@ -0,0 +1,26 @@
|
||||
// Copyright (C) 2014, andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
#include "boost/optional.hpp"
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
//
|
||||
// THIS TEST SHOULD FAIL TO COMPILE
|
||||
//
|
||||
void optional_reference__test_no_assign_from_Trefref()
|
||||
{
|
||||
boost::optional<const int&> opt;
|
||||
opt = int(3);
|
||||
}
|
||||
|
||||
#else
|
||||
# error "Test skipped. This cannot be implemented w/o rvalue references."
|
||||
#endif
|
||||
26
test/optional_test_ref_fail_assign_from_Urefref.cpp
Normal file
26
test/optional_test_ref_fail_assign_from_Urefref.cpp
Normal file
@ -0,0 +1,26 @@
|
||||
// Copyright (C) 2014, andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
#include "boost/optional.hpp"
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
//
|
||||
// THIS TEST SHOULD FAIL TO COMPILE
|
||||
//
|
||||
void optional_reference__test_no_assign_from_Urefref()
|
||||
{
|
||||
boost::optional<const int&> opt;
|
||||
opt = long(3);
|
||||
}
|
||||
|
||||
#else
|
||||
# error "Test skipped. This cannot be implemented w/o rvalue references."
|
||||
#endif
|
||||
25
test/optional_test_ref_fail_init_from_Trefref.cpp
Normal file
25
test/optional_test_ref_fail_init_from_Trefref.cpp
Normal file
@ -0,0 +1,25 @@
|
||||
// Copyright (C) 2014, andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
#include "boost/optional.hpp"
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
//
|
||||
// THIS TEST SHOULD FAIL TO COMPILE
|
||||
//
|
||||
void optional_reference__test_no_init_from_Trefref()
|
||||
{
|
||||
boost::optional<const int&> opt = int(3);
|
||||
}
|
||||
|
||||
#else
|
||||
# error "Test skipped. This cannot be implemented w/o rvalue references."
|
||||
#endif
|
||||
25
test/optional_test_ref_fail_init_from_Urefref.cpp
Normal file
25
test/optional_test_ref_fail_init_from_Urefref.cpp
Normal file
@ -0,0 +1,25 @@
|
||||
// Copyright (C) 2014, andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
#include "boost/optional.hpp"
|
||||
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
//
|
||||
// THIS TEST SHOULD FAIL TO COMPILE
|
||||
//
|
||||
void optional_reference__test_no_init_from_Urefref()
|
||||
{
|
||||
boost::optional<const int&> opt = long(3);
|
||||
}
|
||||
|
||||
#else
|
||||
# error "Test skipped. This cannot be implemented w/o rvalue references."
|
||||
#endif
|
||||
108
test/optional_test_the_compiler.cpp
Normal file
108
test/optional_test_the_compiler.cpp
Normal file
@ -0,0 +1,108 @@
|
||||
// Copyright (C) 2014 Andrzej Krzemienski.
|
||||
//
|
||||
// Use, modification, and distribution is subject to the Boost Software
|
||||
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// akrzemi1@gmail.com
|
||||
//
|
||||
// Revisions:
|
||||
//
|
||||
#include<iostream>
|
||||
#include<stdexcept>
|
||||
//#include<string>
|
||||
|
||||
#define BOOST_ENABLE_ASSERT_HANDLER
|
||||
|
||||
//#include "boost/bind/apply.hpp" // Included just to test proper interaction with boost::apply<> as reported by Daniel Wallin
|
||||
#include "boost/mpl/bool.hpp"
|
||||
#include "boost/mpl/bool_fwd.hpp" // For mpl::true_ and mpl::false_
|
||||
#include "boost/static_assert.hpp"
|
||||
|
||||
#include "boost/optional/optional.hpp"
|
||||
|
||||
#ifdef __BORLANDC__
|
||||
#pragma hdrstop
|
||||
#endif
|
||||
|
||||
#include "boost/test/minimal.hpp"
|
||||
#include "optional_test_common.cpp"
|
||||
|
||||
|
||||
const int global_i = 0;
|
||||
|
||||
class TestingReferenceBinding
|
||||
{
|
||||
public:
|
||||
TestingReferenceBinding(const int& ii)
|
||||
{
|
||||
BOOST_CHECK(&ii == &global_i);
|
||||
}
|
||||
|
||||
void operator=(const int& ii)
|
||||
{
|
||||
BOOST_CHECK(&ii == &global_i);
|
||||
}
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
void operator=(int&&)
|
||||
{
|
||||
BOOST_CHECK(false);
|
||||
}
|
||||
#endif
|
||||
};
|
||||
|
||||
class TestingReferenceBinding2 // same definition as above, I need a different type
|
||||
{
|
||||
public:
|
||||
TestingReferenceBinding2(const int& ii)
|
||||
{
|
||||
BOOST_CHECK(&ii == &global_i);
|
||||
}
|
||||
|
||||
void operator=(const int& ii)
|
||||
{
|
||||
BOOST_CHECK(&ii == &global_i);
|
||||
}
|
||||
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
|
||||
void operator=(int&&)
|
||||
{
|
||||
BOOST_CHECK(false);
|
||||
}
|
||||
#endif
|
||||
};
|
||||
|
||||
|
||||
void test_broken_compiler()
|
||||
{
|
||||
// we are not testing boost::optional here, but the c++ compiler
|
||||
// if this test fails, optional references will obviously fail too
|
||||
|
||||
const int& iref = global_i;
|
||||
BOOST_CHECK(&iref == &global_i);
|
||||
|
||||
TestingReferenceBinding ttt = global_i;
|
||||
ttt = global_i;
|
||||
|
||||
TestingReferenceBinding2 ttt2 = iref;
|
||||
ttt2 = iref;
|
||||
}
|
||||
|
||||
|
||||
int test_main( int, char* [] )
|
||||
{
|
||||
try
|
||||
{
|
||||
test_broken_compiler();
|
||||
}
|
||||
catch ( ... )
|
||||
{
|
||||
BOOST_ERROR("Unexpected Exception caught!");
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
||||
Reference in New Issue
Block a user