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@ -21,10 +21,8 @@ boostbook standalone
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:
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optional
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<a name="boost_optional.a_note_about_optional_bool_"></a><a class="link" href="a_note_about_optional_bool_.html" title="A note about optional<bool>">A note about
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<a name="boost_optional.a_note_about_optional_bool_"></a><a href="a_note_about_optional_bool_.html" title="A note about
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optional<bool>">A note about
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optional<bool></a>
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</h2></div></div></div>
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<p>
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@ -33,7 +36,7 @@
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</p>
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<p>
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First, it is functionally similar to a tristate boolean (false,maybe,true)
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—such as <a href="../../../../../doc/html/tribool.html" target="_top">boost::tribool</a>—
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—such as <a href="../../../../tribool/index.html" target="_top">boost::tribool</a>—
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except that in a tristate boolean, the maybe state <span class="underline">represents
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a valid value</span>, unlike the corresponding state of an uninitialized
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<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">bool</span><span class="special">></span></code>. It
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@ -49,7 +52,8 @@
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lead to subtle errors due to the implicit <code class="computeroutput"><span class="keyword">bool</span></code>
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conversion:
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</p>
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<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
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<pre class="programlisting">
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<span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
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<span class="keyword">void</span> <span class="identifier">bar</span><span class="special">()</span>
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<span class="special">{</span>
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<span class="identifier">optional</span><span class="special"><</span><span class="keyword">bool</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="keyword">try</span><span class="special">();</span>
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@ -70,15 +74,11 @@
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
|
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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>)
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</p>
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</div></td>
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<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
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@ -3,31 +3,32 @@
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<a name="boost_optional.acknowledgments.pre_formal_review"></a><h4>
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<a name="id2865262"></a>
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<a class="link" href="acknowledgments.html#boost_optional.acknowledgments.pre_formal_review">Pre-formal
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<a href="acknowledgments.html#boost_optional.acknowledgments.pre_formal_review">Pre-formal
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</h4>
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<div class="itemizedlist"><ul type="disc">
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@ -65,8 +66,8 @@
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</li>
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</ul></div>
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<a name="boost_optional.acknowledgments.post_formal_review"></a><h4>
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<a name="id2865331"></a>
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<a class="link" href="acknowledgments.html#boost_optional.acknowledgments.post_formal_review">Post-formal
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<a name="id2644931"></a>
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<a href="acknowledgments.html#boost_optional.acknowledgments.post_formal_review">Post-formal
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review</a>
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</h4>
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<div class="itemizedlist"><ul type="disc">
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@ -111,15 +112,11 @@
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="right"><div class="copyright-footer">Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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>)
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@ -34,15 +36,11 @@
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<td align="right"><div class="copyright-footer">Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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>)
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|
||||
<a accesskey="p" href="synopsis.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="examples.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
|
||||
<a accesskey="p" href="synopsis.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="examples.html"><img src="../images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.detailed_semantics"></a><a class="link" href="detailed_semantics.html" title="Detailed Semantics">Detailed Semantics</a>
|
||||
<a name="boost_optional.detailed_semantics"></a><a href="detailed_semantics.html" title="Detailed Semantics">Detailed Semantics</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
Because <code class="computeroutput"><span class="identifier">T</span></code> might be of reference
|
||||
type, in the sequel, those entries whose semantic depends on <code class="computeroutput"><span class="identifier">T</span></code> being of reference type or not will be
|
||||
distinguished using the following convention:
|
||||
distinguished using the following convention: * If the entry reads: <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></code>, the description corresponds only to the
|
||||
case where <code class="computeroutput"><span class="identifier">T</span></code> is not of reference
|
||||
type. * If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>,
|
||||
the description corresponds only to the case where <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
is of reference type. * If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>,
|
||||
the description is the same for both cases.
|
||||
</p>
|
||||
<div class="itemizedlist"><ul type="disc">
|
||||
<li>
|
||||
If the entry reads: <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></code>, the description
|
||||
corresponds only to the case where <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
is not of reference type.
|
||||
</li>
|
||||
<li>
|
||||
If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>,
|
||||
the description corresponds only to the case where <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
is of reference type.
|
||||
</li>
|
||||
<li>
|
||||
If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>,
|
||||
the description is the same for both cases.
|
||||
</li>
|
||||
</ul></div>
|
||||
<div class="note"><table border="0" summary="Note">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/html/images/note.png"></td>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../images/note.png"></td>
|
||||
<th align="left">Note</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
The following section contains various <code class="computeroutput"><span class="identifier">assert</span><span class="special">()</span></code> which are used only to show the postconditions
|
||||
as sample code. It is not implied that the type <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
must support each particular expression but that if the expression is supported,
|
||||
the implied condition holds.
|
||||
</p></td></tr>
|
||||
<tr><td align="left" valign="top">
|
||||
<p>
|
||||
</p>
|
||||
<p>
|
||||
The following section contains various <code class="computeroutput"><span class="identifier">assert</span><span class="special">()</span></code> which are used only to show the postconditions
|
||||
as sample code. It is not implied that the type <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
must support each particular expression but that if the expression is supported,
|
||||
the implied condition holds.
|
||||
</p>
|
||||
<p>
|
||||
</p>
|
||||
</td></tr>
|
||||
</table></div>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="boost_optional.detailed_semantics.optional_class_member_functions"></a><h4>
|
||||
<a name="id2841077"></a>
|
||||
<a class="link" href="detailed_semantics.html#boost_optional.detailed_semantics.optional_class_member_functions">optional
|
||||
<a name="id2620116"></a>
|
||||
<a href="detailed_semantics.html#boost_optional.detailed_semantics.optional_class_member_functions">optional
|
||||
class member functions</a>
|
||||
</h4>
|
||||
<p>
|
||||
@ -97,7 +91,8 @@
|
||||
called.
|
||||
</li>
|
||||
<li>
|
||||
<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>
|
||||
<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>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
</li>
|
||||
@ -133,7 +128,8 @@
|
||||
The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code> denotes an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code> that can be used as the parameter.
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">none</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting">
|
||||
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">none</span><span class="special">.</span><span class="identifier">hpp</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">n</span><span class="special">(</span><span class="identifier">none</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">n</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
@ -178,7 +174,8 @@
|
||||
has no effect.
|
||||
</li>
|
||||
<li>
|
||||
<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="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">opt</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">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
|
||||
</pre>
|
||||
@ -209,7 +206,8 @@
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li>
|
||||
<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="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">T</span><span class="special">&</span> <span class="identifier">vref</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">T</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">vref</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">v</span> <span class="special">)</span> <span class="special">;</span>
|
||||
@ -334,7 +332,8 @@
|
||||
has no effect.
|
||||
</li>
|
||||
<li>
|
||||
<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">uninit</span> <span class="special">;</span>
|
||||
<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">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">T</span><span class="special">></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
|
||||
@ -382,7 +381,8 @@
|
||||
will reefer to the same object (they alias).
|
||||
</li>
|
||||
<li>
|
||||
<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">uninit</span> <span class="special">;</span>
|
||||
<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">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">T</span><span class="special">&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
|
||||
@ -448,7 +448,8 @@
|
||||
has no effect.
|
||||
</li>
|
||||
<li>
|
||||
<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="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">x</span><span class="special">)</span> <span class="special">;</span>
|
||||
@ -499,7 +500,7 @@
|
||||
constructor called by the factory throws.
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../index.html#optional_in_place_factories">In-Place
|
||||
<span class="bold"><strong>Notes:</strong></span> See <a href="../index.html#optional_in_place_factories">In-Place
|
||||
Factories</a>
|
||||
</li>
|
||||
<li>
|
||||
@ -508,7 +509,8 @@
|
||||
constructor used by the factory; in that case, this constructor has no effect.
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting"><span class="keyword">class</span> <span class="identifier">C</span> <span class="special">{</span> <span class="identifier">C</span> <span class="special">(</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting">
|
||||
<span class="keyword">class</span> <span class="identifier">C</span> <span class="special">{</span> <span class="identifier">C</span> <span class="special">(</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
|
||||
|
||||
<span class="identifier">C</span> <span class="identifier">v</span><span class="special">(</span><span class="char">'A'</span><span class="special">,</span><span class="number">123.4</span><span class="special">,</span><span class="string">"hello"</span><span class="special">);</span>
|
||||
|
||||
@ -566,7 +568,8 @@
|
||||
<span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
||||
</li>
|
||||
<li>
|
||||
<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="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>
|
||||
|
||||
@ -604,11 +607,12 @@
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, is is <span class="emphasis"><em>rebound</em></span>
|
||||
to the new object. See <a class="link" href="../index.html#optional_refassign">here</a> for
|
||||
to the new object. See <a href="../index.html#optional_refassign">here</a> for
|
||||
details on this behavior.
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting">
|
||||
<span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
|
||||
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
|
||||
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
|
||||
@ -677,7 +681,8 @@
|
||||
<span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
||||
</li>
|
||||
<li>
|
||||
<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="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">opt</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">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
|
||||
|
||||
@ -710,11 +715,12 @@
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized and so is *rhs, this
|
||||
is is <span class="emphasis"><em>rebound</em></span> to the new object. See <a class="link" href="../index.html#optional_refassign">here</a>
|
||||
is is <span class="emphasis"><em>rebound</em></span> to the new object. See <a href="../index.html#optional_refassign">here</a>
|
||||
for details on this behavior.
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting">
|
||||
<span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
|
||||
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
|
||||
<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
|
||||
@ -788,7 +794,8 @@
|
||||
converting constructor fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
|
||||
</li>
|
||||
<li>
|
||||
<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="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>
|
||||
|
||||
@ -917,7 +924,8 @@
|
||||
<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
|
||||
</li>
|
||||
<li>
|
||||
<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="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">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
|
||||
<span class="identifier">assert</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>
|
||||
@ -991,7 +999,8 @@
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li>
|
||||
<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">z</span> <span class="special">;</span>
|
||||
<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">z</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">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">=</span> <span class="identifier">def</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">y</span> <span class="special">==</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
|
||||
@ -1084,7 +1093,8 @@
|
||||
<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
|
||||
</li>
|
||||
<li>
|
||||
<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="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">T</span><span class="special">&</span> <span class="identifier">vref</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">T</span><span class="special">&></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">vref</span> <span class="special">);</span>
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">vref2</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
|
||||
@ -1157,7 +1167,8 @@
|
||||
so you should not hold nor delete this pointer
|
||||
</li>
|
||||
<li>
|
||||
<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="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">opt</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">T</span><span class="special">></span> <span class="keyword">const</span> <span class="identifier">copt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
|
||||
<span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span>
|
||||
@ -1209,7 +1220,8 @@
|
||||
<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> <span class="keyword">int</span> <span class="identifier">mdata</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting">
|
||||
<span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> <span class="keyword">int</span> <span class="identifier">mdata</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
|
||||
<span class="identifier">X</span> <span class="identifier">x</span> <span class="special">;</span>
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">X</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="identifier">opt</span><span class="special">-></span><span class="identifier">mdata</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
|
||||
@ -1239,7 +1251,8 @@
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li>
|
||||
<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>
|
||||
<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>
|
||||
<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</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="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</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>
|
||||
@ -1275,7 +1288,8 @@
|
||||
in certain boolean contexts.
|
||||
</li>
|
||||
<li>
|
||||
<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="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">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">opt</span> <span class="special">=</span> <span class="identifier">some_T</span> <span class="special">;</span>
|
||||
|
||||
@ -1308,7 +1322,8 @@
|
||||
<span class="bold"><strong>Throws:</strong></span> Nothing.
|
||||
</li>
|
||||
<li>
|
||||
<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>
|
||||
<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>
|
||||
<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">is_initialized</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">opt</span> <span class="special">(</span> <span class="identifier">v</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="identifier">is_initialized</span><span class="special">()</span> <span class="special">);</span>
|
||||
@ -1319,8 +1334,8 @@
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
</p>
|
||||
<a name="boost_optional.detailed_semantics.free_functions"></a><h4>
|
||||
<a name="id2853708"></a>
|
||||
<a class="link" href="detailed_semantics.html#boost_optional.detailed_semantics.free_functions">Free functions</a>
|
||||
<a name="id2633284"></a>
|
||||
<a href="detailed_semantics.html#boost_optional.detailed_semantics.free_functions">Free functions</a>
|
||||
</h4>
|
||||
<p>
|
||||
<span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
|
||||
@ -1343,7 +1358,8 @@
|
||||
of <code class="computeroutput"><span class="identifier">v</span></code>.
|
||||
</li>
|
||||
<li>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting"><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">void</span> <span class="identifier">foo</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">opt</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="bold"><strong>Example:</strong></span><pre class="programlisting">
|
||||
<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">void</span> <span class="identifier">foo</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">opt</span> <span class="special">)</span> <span class="special">;</span>
|
||||
|
||||
<span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional<int>
|
||||
</span></pre>
|
||||
@ -1371,7 +1387,8 @@
|
||||
of <code class="computeroutput"><span class="identifier">v</span></code>.
|
||||
</li>
|
||||
<li>
|
||||
<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">calculate_foo</span><span class="special">()</span>
|
||||
<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">calculate_foo</span><span class="special">()</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span>
|
||||
<span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span>
|
||||
@ -1418,7 +1435,8 @@
|
||||
instead
|
||||
</li>
|
||||
<li>
|
||||
<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="number">12</span><span class="special">);</span>
|
||||
<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="number">12</span><span class="special">);</span>
|
||||
<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
|
||||
<span class="identifier">T</span> <span class="identifier">z</span><span class="special">(</span><span class="number">21</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">def0</span> <span class="special">;</span>
|
||||
@ -1479,7 +1497,8 @@
|
||||
instead.
|
||||
</li>
|
||||
<li>
|
||||
<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="number">12</span><span class="special">);</span>
|
||||
<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="number">12</span><span class="special">);</span>
|
||||
<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">34</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">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
|
||||
@ -1649,7 +1668,8 @@
|
||||
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>.
|
||||
</li>
|
||||
<li>
|
||||
<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="number">12</span><span class="special">);</span>
|
||||
<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="number">12</span><span class="special">);</span>
|
||||
<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</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">def0</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">def1</span> <span class="special">;</span>
|
||||
@ -1673,15 +1693,11 @@
|
||||
</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 <20> 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="synopsis.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="examples.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
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||||
<a accesskey="p" href="synopsis.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="examples.html"><img src="../images/next.png" alt="Next"></a>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@ -3,28 +3,28 @@
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
||||
<title>Development</title>
|
||||
<link rel="stylesheet" href="../boostbook.css" type="text/css">
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2">
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<meta name="generator" content="DocBook XSL Stylesheets V1.70.1">
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<link rel="start" href="../index.html" title="Chapter<65>1.<2E>Boost.Optional">
|
||||
<link rel="up" href="../index.html" title="Chapter<65>1.<2E>Boost.Optional">
|
||||
<link rel="prev" href="../index.html" title="Chapter<65>1.<2E>Boost.Optional">
|
||||
<link rel="next" href="synopsis.html" title="Synopsis">
|
||||
</head>
|
||||
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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<table cellpadding="2" width="100%"><tr>
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<td align="center"><a href="../../../../libraries.htm">Libraries</a></td>
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<a accesskey="p" href="../index.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="synopsis.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
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<a accesskey="p" href="../index.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="synopsis.html"><img src="../images/next.png" alt="Next"></a>
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</div>
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<div class="section" lang="en">
|
||||
<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>
|
||||
<a name="boost_optional.development"></a><a href="development.html" title="Development">Development</a>
|
||||
</h2></div></div></div>
|
||||
<div class="toc"><dl>
|
||||
<dt><span class="section"><a href="development.html#boost_optional.development.the_models">The models</a></span></dt>
|
||||
@ -33,7 +33,7 @@
|
||||
</dl></div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_optional.development.the_models"></a><a class="link" href="development.html#boost_optional.development.the_models" title="The models">The models</a>
|
||||
<a name="boost_optional.development.the_models"></a><a href="development.html#boost_optional.development.the_models" title="The models">The models</a>
|
||||
</h3></div></div></div>
|
||||
<p>
|
||||
In C++, we can <span class="emphasis"><em>declare</em></span> an object (a variable) of type
|
||||
@ -170,7 +170,7 @@
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_optional.development.the_semantics"></a><a class="link" href="development.html#boost_optional.development.the_semantics" title="The semantics">The semantics</a>
|
||||
<a name="boost_optional.development.the_semantics"></a><a href="development.html#boost_optional.development.the_semantics" title="The semantics">The semantics</a>
|
||||
</h3></div></div></div>
|
||||
<p>
|
||||
Objects of type <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
|
||||
@ -254,7 +254,7 @@
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_optional.development.the_interface"></a><a class="link" href="development.html#boost_optional.development.the_interface" title="The Interface">The Interface</a>
|
||||
<a name="boost_optional.development.the_interface"></a><a href="development.html#boost_optional.development.the_interface" title="The Interface">The Interface</a>
|
||||
</h3></div></div></div>
|
||||
<p>
|
||||
Since the purpose of optional is to allow us to use objects with a formal
|
||||
@ -292,8 +292,8 @@
|
||||
itself which are supported by a special interface.
|
||||
</p>
|
||||
<a name="boost_optional.development.the_interface.lexically_hinted_value_access_in_the_presence_of_possibly_untitialized_optional_objects__the_operators___and___gt_"></a><h5>
|
||||
<a name="id2836653"></a>
|
||||
<a class="link" href="development.html#boost_optional.development.the_interface.lexically_hinted_value_access_in_the_presence_of_possibly_untitialized_optional_objects__the_operators___and___gt_">Lexically-hinted
|
||||
<a name="id2615242"></a>
|
||||
<a href="development.html#boost_optional.development.the_interface.lexically_hinted_value_access_in_the_presence_of_possibly_untitialized_optional_objects__the_operators___and___gt_">Lexically-hinted
|
||||
Value Access in the presence of possibly untitialized optional objects: The
|
||||
operators * and -></a>
|
||||
</h5>
|
||||
@ -357,8 +357,8 @@
|
||||
incarnated by pointers.
|
||||
</p>
|
||||
<a name="boost_optional.development.the_interface.optional_lt_t_gt__as_a_model_of_optionalpointee"></a><h5>
|
||||
<a name="id2836963"></a>
|
||||
<a class="link" href="development.html#boost_optional.development.the_interface.optional_lt_t_gt__as_a_model_of_optionalpointee">Optional<T>
|
||||
<a name="id2615580"></a>
|
||||
<a href="development.html#boost_optional.development.the_interface.optional_lt_t_gt__as_a_model_of_optionalpointee">Optional<T>
|
||||
as a model of OptionalPointee</a>
|
||||
</h5>
|
||||
<p>
|
||||
@ -369,12 +369,19 @@
|
||||
</p>
|
||||
<div class="warning"><table border="0" summary="Warning">
|
||||
<tr>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../doc/html/images/warning.png"></td>
|
||||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../images/warning.png"></td>
|
||||
<th align="left">Warning</th>
|
||||
</tr>
|
||||
<tr><td align="left" valign="top"><p>
|
||||
However, it is particularly important to note that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code> objects are not pointers. <span class="underline"><code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code> is not, and does not model, a pointer</span>.
|
||||
</p></td></tr>
|
||||
<tr><td align="left" valign="top">
|
||||
<p>
|
||||
</p>
|
||||
<p>
|
||||
However, it is particularly important to note that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code> objects are not pointers. <span class="underline"><code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code> is not, and does not model, a
|
||||
pointer</span>.
|
||||
</p>
|
||||
<p>
|
||||
</p>
|
||||
</td></tr>
|
||||
</table></div>
|
||||
<p>
|
||||
For instance, <code class="computeroutput"><span class="identifier">optional</span><span class="special"><></span></code>
|
||||
@ -398,15 +405,11 @@
|
||||
</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 <20> 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="../index.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="synopsis.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
|
||||
<a accesskey="p" href="../index.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="synopsis.html"><img src="../images/next.png" alt="Next"></a>
|
||||
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|
||||
</body>
|
||||
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|
||||
|
||||
@ -3,28 +3,28 @@
|
||||
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|
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|
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<link rel="prev" href="detailed_semantics.html" title="Detailed Semantics">
|
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<link rel="next" href="optional_references.html" title="Optional references">
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<a accesskey="p" href="detailed_semantics.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="optional_references.html"><img src="../images/next.png" alt="Next"></a>
|
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</div>
|
||||
<div class="section" lang="en">
|
||||
<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>
|
||||
<a name="boost_optional.examples"></a><a href="examples.html" title="Examples">Examples</a>
|
||||
</h2></div></div></div>
|
||||
<div class="toc"><dl>
|
||||
<dt><span class="section"><a href="examples.html#boost_optional.examples.optional_return_values">Optional
|
||||
@ -38,10 +38,12 @@
|
||||
</dl></div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_optional.examples.optional_return_values"></a><a class="link" href="examples.html#boost_optional.examples.optional_return_values" title="Optional return values">Optional
|
||||
<a name="boost_optional.examples.optional_return_values"></a><a href="examples.html#boost_optional.examples.optional_return_values" title="Optional
|
||||
return values">Optional
|
||||
return values</a>
|
||||
</h3></div></div></div>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">char</span><span class="special">></span> <span class="identifier">get_async_input</span><span class="special">()</span>
|
||||
<pre class="programlisting">
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="keyword">char</span><span class="special">></span> <span class="identifier">get_async_input</span><span class="special">()</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">queue</span><span class="special">.</span><span class="identifier">empty</span><span class="special">()</span> <span class="special">)</span>
|
||||
<span class="keyword">return</span> <span class="identifier">optional</span><span class="special"><</span><span class="keyword">char</span><span class="special">>(</span><span class="identifier">queue</span><span class="special">.</span><span class="identifier">top</span><span class="special">());</span>
|
||||
@ -59,10 +61,12 @@
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_optional.examples.optional_local_variables"></a><a class="link" href="examples.html#boost_optional.examples.optional_local_variables" title="Optional local variables">Optional
|
||||
<a name="boost_optional.examples.optional_local_variables"></a><a href="examples.html#boost_optional.examples.optional_local_variables" title="Optional
|
||||
local variables">Optional
|
||||
local variables</a>
|
||||
</h3></div></div></div>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">string</span><span class="special">></span> <span class="identifier">name</span> <span class="special">;</span>
|
||||
<pre class="programlisting">
|
||||
<span class="identifier">optional</span><span class="special"><</span><span class="identifier">string</span><span class="special">></span> <span class="identifier">name</span> <span class="special">;</span>
|
||||
<span class="keyword">if</span> <span class="special">(</span> <span class="identifier">database</span><span class="special">.</span><span class="identifier">open</span><span class="special">()</span> <span class="special">)</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">name</span><span class="special">.</span><span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">database</span><span class="special">.</span><span class="identifier">lookup</span><span class="special">(</span><span class="identifier">employer_name</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
|
||||
@ -80,10 +84,12 @@
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_optional.examples.optional_data_members"></a><a class="link" href="examples.html#boost_optional.examples.optional_data_members" title="Optional data members">Optional
|
||||
<a name="boost_optional.examples.optional_data_members"></a><a href="examples.html#boost_optional.examples.optional_data_members" title="Optional
|
||||
data members">Optional
|
||||
data members</a>
|
||||
</h3></div></div></div>
|
||||
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">figure</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">class</span> <span class="identifier">figure</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">public</span><span class="special">:</span>
|
||||
|
||||
@ -118,10 +124,12 @@
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_optional.examples.bypassing_expensive_unnecessary_default_construction"></a><a class="link" href="examples.html#boost_optional.examples.bypassing_expensive_unnecessary_default_construction" title="Bypassing expensive unnecessary default construction">Bypassing
|
||||
<a name="boost_optional.examples.bypassing_expensive_unnecessary_default_construction"></a><a href="examples.html#boost_optional.examples.bypassing_expensive_unnecessary_default_construction" title="Bypassing
|
||||
expensive unnecessary default construction">Bypassing
|
||||
expensive unnecessary default construction</a>
|
||||
</h3></div></div></div>
|
||||
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">ExpensiveCtor</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span> <span class="special">;</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">class</span> <span class="identifier">ExpensiveCtor</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span> <span class="special">;</span>
|
||||
<span class="keyword">class</span> <span class="identifier">Fred</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">Fred</span><span class="special">()</span> <span class="special">:</span> <span class="identifier">mLargeVector</span><span class="special">(</span><span class="number">10000</span><span class="special">)</span> <span class="special">{}</span>
|
||||
@ -133,15 +141,11 @@
|
||||
</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 <20> 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="detailed_semantics.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="optional_references.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
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||||
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||||
|
||||
@ -1,34 +1,37 @@
|
||||
<html>
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||||
<head>
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||||
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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|
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="boost_optional.exception_safety_guarantees"></a><a class="link" href="exception_safety_guarantees.html" title="Exception Safety Guarantees">Exception Safety
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<a name="boost_optional.exception_safety_guarantees"></a><a href="exception_safety_guarantees.html" title="Exception Safety
|
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Guarantees">Exception Safety
|
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Guarantees</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
Because of the current implementation (see <a class="link" href="../index.html#optional_implementation_notes">Implementation
|
||||
Because of the current implementation (see <a href="../index.html#optional_implementation_notes">Implementation
|
||||
Notes</a>), all of the assignment methods:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul type="disc">
|
||||
@ -72,7 +75,8 @@
|
||||
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">//
|
||||
<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>
|
||||
@ -112,8 +116,8 @@
|
||||
<span class="special">}</span>
|
||||
</pre>
|
||||
<a name="boost_optional.exception_safety_guarantees.swap"></a><h4>
|
||||
<a name="id2864737"></a>
|
||||
<a class="link" href="exception_safety_guarantees.html#boost_optional.exception_safety_guarantees.swap">Swap</a>
|
||||
<a name="id2644335"></a>
|
||||
<a 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>
|
||||
@ -126,15 +130,11 @@
|
||||
</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 <20> 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
||||
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|
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</h2></div></div></div>
|
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<p>
|
||||
<code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is
|
||||
@ -41,15 +42,11 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
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<td align="right"><div class="copyright-footer">Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal<p>
|
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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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
||||
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@ -3,28 +3,30 @@
|
||||
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|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
One of the typical problems with wrappers and containers is that their interfaces
|
||||
@ -34,7 +36,8 @@
|
||||
but also requires the existence of a fully constructed object, often temporary,
|
||||
just to follow the copy from:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">struct</span> <span class="identifier">X</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">X</span> <span class="special">(</span> <span class="keyword">int</span><span class="special">,</span> <span class="identifier">std</span><span class="special">:::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span>
|
||||
<span class="special">}</span> <span class="special">;</span>
|
||||
@ -59,7 +62,8 @@
|
||||
object right in the container's storage. In this scheme, the user only needs
|
||||
to supply the arguments to the constructor to use in the wrapped object construction.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">W</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">class</span> <span class="identifier">W</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">X</span> <span class="identifier">wrapped_</span> <span class="special">;</span>
|
||||
|
||||
@ -92,7 +96,8 @@
|
||||
<p>
|
||||
For example, one member of this family looks like:
|
||||
</p>
|
||||
<pre class="programlisting"><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">class</span> <span class="identifier">A0</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">A1</span><span class="special">></span>
|
||||
<pre class="programlisting">
|
||||
<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">class</span> <span class="identifier">A0</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">A1</span><span class="special">></span>
|
||||
<span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory2</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">A0</span> <span class="identifier">m_a0</span> <span class="special">;</span> <span class="identifier">A1</span> <span class="identifier">m_a1</span> <span class="special">;</span>
|
||||
@ -107,7 +112,8 @@
|
||||
<p>
|
||||
A wrapper class aware of this can use it as:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">W</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">class</span> <span class="identifier">W</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">X</span> <span class="identifier">wrapped_</span> <span class="special">;</span>
|
||||
|
||||
@ -146,7 +152,8 @@
|
||||
This library provides an overloaded set of helper template functions to construct
|
||||
these factories without requiring unnecessary template parameters:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">A0</span><span class="special">,...,</span><span class="keyword">class</span> <span class="identifier">AN</span><span class="special">></span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">A0</span><span class="special">,...,</span><span class="keyword">class</span> <span class="identifier">AN</span><span class="special">></span>
|
||||
<span class="identifier">InPlaceFactoryN</span> <span class="special"><</span><span class="identifier">A0</span><span class="special">,...,</span><span class="identifier">AN</span><span class="special">></span> <span class="identifier">in_place</span> <span class="special">(</span> <span class="identifier">A0</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">a0</span><span class="special">,</span> <span class="special">...,</span> <span class="identifier">AN</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">aN</span><span class="special">)</span> <span class="special">;</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">class</span> <span class="identifier">A0</span><span class="special">,...,</span><span class="keyword">class</span> <span class="identifier">AN</span><span class="special">></span>
|
||||
@ -155,7 +162,8 @@
|
||||
<p>
|
||||
In-place factories can be used generically by the wrapper and user as follows:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">W</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">class</span> <span class="identifier">W</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">X</span> <span class="identifier">wrapped_</span> <span class="special">;</span>
|
||||
|
||||
@ -182,15 +190,11 @@
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
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<td align="left"></td>
|
||||
<td align="right"><div class="copyright-footer">Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
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|
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||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.optional_references"></a><a class="link" href="optional_references.html" title="Optional references">Optional references</a>
|
||||
<a name="boost_optional.optional_references"></a><a href="optional_references.html" title="Optional references">Optional references</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
This library allows the template parameter <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
@ -71,15 +72,11 @@
|
||||
</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 <20> 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
||||
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||||
<hr>
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||||
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||||
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|
||||
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<title>Rebinding
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semantics for assignment of optional references</title>
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<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.rebinding_semantics_for_assignment_of_optional_references"></a><a class="link" href="rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">Rebinding
|
||||
<a name="boost_optional.rebinding_semantics_for_assignment_of_optional_references"></a><a href="rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding
|
||||
semantics for assignment of optional references">Rebinding
|
||||
semantics for assignment of optional references</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
@ -32,7 +34,8 @@
|
||||
the effect is to bind (for the first time) to the object. Clearly, there is
|
||||
no other choice.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">x</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">int</span> <span class="identifier">x</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rx</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="keyword">int</span><span class="special">&></span> <span class="identifier">ora</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">orb</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
|
||||
@ -44,7 +47,8 @@
|
||||
If you assign to a bare C++ reference, the assignment is forwarded to the referenced
|
||||
object; it's value changes but the reference is never rebound.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
|
||||
@ -58,7 +62,8 @@
|
||||
the effect is to <span class="bold"><strong>rebind</strong></span> to the new object
|
||||
instead of assigning the referee. This is unlike bare C++ references.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
|
||||
@ -70,8 +75,8 @@
|
||||
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">b</span><span class="special">==</span><span class="number">3</span><span class="special">);</span>
|
||||
</pre>
|
||||
<a name="boost_optional.rebinding_semantics_for_assignment_of_optional_references.rationale"></a><h4>
|
||||
<a name="id2860344"></a>
|
||||
<a class="link" href="rebinding_semantics_for_assignment_of_optional_references.html#boost_optional.rebinding_semantics_for_assignment_of_optional_references.rationale">Rationale</a>
|
||||
<a name="id2639932"></a>
|
||||
<a href="rebinding_semantics_for_assignment_of_optional_references.html#boost_optional.rebinding_semantics_for_assignment_of_optional_references.rationale">Rationale</a>
|
||||
</h4>
|
||||
<p>
|
||||
Rebinding semantics for the assignment of <span class="emphasis"><em>initialized </em></span>
|
||||
@ -90,7 +95,8 @@
|
||||
forwarding assignment to the referenced object (thus changing the referenced
|
||||
object value but not rebinding), and consider the following code:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">a</span> <span class="special">=</span> <span class="identifier">get</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">a</span> <span class="special">=</span> <span class="identifier">get</span><span class="special">();</span>
|
||||
<span class="keyword">int</span> <span class="identifier">x</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
|
||||
<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rx</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="keyword">int</span><span class="special">&></span> <span class="identifier">b</span><span class="special">(</span><span class="identifier">rx</span><span class="special">);</span>
|
||||
@ -128,21 +134,18 @@
|
||||
for the first time is OK while rebinding is not which is IMO very unlikely.
|
||||
In such scenario, you can assign the value itself directly, as in:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">assert</span><span class="special">(!!</span><span class="identifier">opt</span><span class="special">);</span>
|
||||
<pre class="programlisting">
|
||||
<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">opt</span><span class="special">=</span><span class="identifier">value</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 <20> 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="optional_references.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="in_place_factories.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
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|
||||
@ -3,30 +3,31 @@
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
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<title>Synopsis</title>
|
||||
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|
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|
||||
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|
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<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_optional.synopsis"></a><a class="link" href="synopsis.html" title="Synopsis">Synopsis</a>
|
||||
<a name="boost_optional.synopsis"></a><a href="synopsis.html" title="Synopsis">Synopsis</a>
|
||||
</h2></div></div></div>
|
||||
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
|
||||
<pre class="programlisting">
|
||||
<span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</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">class</span> <span class="identifier">optional</span>
|
||||
@ -35,116 +36,112 @@
|
||||
|
||||
<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="special">;</span> <a 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="special">;</span> <a 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="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_constructor_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> <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 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="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_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="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a 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">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">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 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="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 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">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="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a 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">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="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_operator_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="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a 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">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>
|
||||
|
||||
<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>
|
||||
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get"><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</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get"><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</span><span class="special">()</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="comment">// [new in 1.34]
|
||||
</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get_value_or_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get_value_or_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</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_arrow"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">->()</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">->()</span> <span class="keyword">const</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">->()</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</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_get"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="keyword">const</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
<span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<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="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 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 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">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 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="special">;</span> <a 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> <span class="keyword">void</span> <span class="identifier">reset</span><span class="special">()</span> <span class="special">;</span> <a 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>
|
||||
</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 href="detailed_semantics.html#reference_optional_reset_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="comment">// (deprecated)
|
||||
</span> <span class="keyword">bool</span> <span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_is_initialized"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
</span> <span class="keyword">bool</span> <span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_is_initialized"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="special">};</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="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_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">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 href="detailed_semantics.html#reference_operator_compare_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">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_not_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">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 href="detailed_semantics.html#reference_operator_compare_not_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">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_less_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">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 href="detailed_semantics.html#reference_operator_compare_less_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">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_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">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 href="detailed_semantics.html#reference_operator_compare_greater_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">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_less_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">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 href="detailed_semantics.html#reference_operator_compare_less_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">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">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 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="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>
|
||||
</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 href="detailed_semantics.html#reference_make_optional_value"><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="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_make_optional_bool_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
</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="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 href="detailed_semantics.html#reference_make_optional_bool_value"><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">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get_optional_value_or</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">opt</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get_value_or_value"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
</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">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get_optional_value_or</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">opt</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get_value_or_value"><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="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get</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">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get"><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="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get</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">opt</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get"><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="identifier">T</span><span class="special">&</span> <span class="identifier">get</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> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get"><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="identifier">T</span><span class="special">&</span> <span class="identifier">get</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> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get"><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="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get</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">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get"><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="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get</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">opt</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get"><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="identifier">T</span><span class="special">*</span> <span class="identifier">get</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="special">;</span> <a class="link" href="detailed_semantics.html#reference_optional_get"><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="identifier">T</span><span class="special">*</span> <span class="identifier">get</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="special">;</span> <a href="detailed_semantics.html#reference_optional_get"><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="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_pointer</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">opt</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">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">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_pointer</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">opt</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get_ptr"><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="identifier">T</span><span class="special">*</span> <span class="identifier">get_pointer</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> <span class="identifier">opt</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">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">T</span><span class="special">*</span> <span class="identifier">get_pointer</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> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a href="detailed_semantics.html#reference_optional_get_ptr"><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">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> <span class="special">;</span> <a class="link" href="detailed_semantics.html#reference_swap_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">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> <span class="special">;</span> <a href="detailed_semantics.html#reference_swap_optional_optional"><span class="inlinemediaobject"><img src="../images/callouts/R.png" alt="R"></span></a>
|
||||
|
||||
<span class="special">}</span> <span class="comment">// namespace boost
|
||||
</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 <20> 2003 -2007 Fernando Luis Cacciola Carballal<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>
|
||||
<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav">
|
||||
<a accesskey="p" href="development.html"><img src="../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics.html"><img src="../../../../../doc/html/images/next.png" alt="Next"></a>
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In general, <code class="computeroutput"><span class="identifier">T</span></code> must be <a href="../../../../utility/CopyConstructible.html" target="_top">Copy Constructible</a> and
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<td align="right"><div class="copyright-footer">Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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>)
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<td align="right"><small>Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</small></td>
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0
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<div><h2 class="title">
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@ -27,7 +27,7 @@
|
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</h3></div></div>
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<div><p class="copyright">Copyright <20> 2003 -2007 Fernando Luis Cacciola Carballal</p></div>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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|
||||
@ -38,24 +38,9 @@
|
||||
<dl>
|
||||
<dt><span class="section"><a href="index.html#optional.motivation">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>
|
||||
<dt><span class="section"><a href="boost_optional/development.html#boost_optional.development.the_semantics">The semantics</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/development.html#boost_optional.development.the_interface">The Interface</a></span></dt>
|
||||
</dl></dd>
|
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<dt><span class="section"><a href="boost_optional/synopsis.html">Synopsis</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/detailed_semantics.html">Detailed Semantics</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/examples.html">Examples</a></span></dt>
|
||||
<dd><dl>
|
||||
<dt><span class="section"><a href="boost_optional/examples.html#boost_optional.examples.optional_return_values">Optional
|
||||
return values</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/examples.html#boost_optional.examples.optional_local_variables">Optional
|
||||
local variables</a></span></dt>
|
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<dt><span class="section"><a href="boost_optional/examples.html#boost_optional.examples.optional_data_members">Optional
|
||||
data members</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/examples.html#boost_optional.examples.bypassing_expensive_unnecessary_default_construction">Bypassing
|
||||
expensive unnecessary default construction</a></span></dt>
|
||||
</dl></dd>
|
||||
<dt><span class="section"><a href="boost_optional/optional_references.html">Optional references</a></span></dt>
|
||||
<dt><span class="section"><a href="boost_optional/rebinding_semantics_for_assignment_of_optional_references.html">Rebinding
|
||||
semantics for assignment of optional references</a></span></dt>
|
||||
@ -73,7 +58,7 @@
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<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.motivation"></a><a href="index.html#optional.motivation" title="Motivation">Motivation</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
Consider these functions which should return a value but which might not have
|
||||
@ -142,14 +127,16 @@
|
||||
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>
|
||||
<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 inexistent
|
||||
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>
|
||||
<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>
|
||||
@ -172,10 +159,10 @@
|
||||
</p>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"><p><small>Last revised: October 10, 2008 at 20:53:37 GMT</small></p></td>
|
||||
<td align="right"><div class="copyright-footer"></div></td>
|
||||
<td align="left"><small><p>Last revised: May 29, 2007 at 06:31:03 GMT</p></small></td>
|
||||
<td align="right"><small></small></td>
|
||||
</tr></table>
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|
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</html>
|
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|
||||
@ -3,6 +3,7 @@
|
||||
<HTML>
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|
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<HEAD>
|
||||
<meta http-equiv="Content-Language" content="en-us">
|
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<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
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<meta name="ProgId" content="FrontPage.Editor.Document">
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=windows-1252">
|
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@ -23,6 +24,7 @@ HREF="../../../boost/optional/optional.hpp">boost/optional/optional.hpp</A>>
|
||||
<DT><A HREF="#examples">Examples</A></DT>
|
||||
<DT><A HREF="#ref">Optional references</A></DT>
|
||||
<DT><A HREF="#refassign">Rebinding semantics for assignment of optional references</A></DT>
|
||||
<DT><A HREF="#none">none_t and none</A></DT>
|
||||
<DT><A HREF="#inplace">In-Place Factories</A></DT>
|
||||
<DT><A HREF="#bool">A note about optional<bool></A></DT>
|
||||
<DT><A HREF="#exsafety">Exception Safety Guarantees</A></DT>
|
||||
@ -138,7 +140,7 @@ necessary in order to do so.</p>
|
||||
<u>purpose</u> of optional<T> suggests
|
||||
an alternative model: a <i>container</i> that either has a value of T or nothing.
|
||||
</p>
|
||||
<p>As of this writing I don't know of any precedence for a variable-size fixed-capacity (of 1)
|
||||
<p>As of this writing I don't know of any precedent for a variable-size fixed-capacity (of 1)
|
||||
stack-based container model for optional values, yet I believe this is the consequence of
|
||||
the lack of practical implementations of such a container rather than an inherent shortcoming
|
||||
of the container model.</p>
|
||||
@ -329,9 +331,9 @@ class optional
|
||||
|
||||
template<class U> explicit optional ( optional<U> const& rhs ) ;
|
||||
|
||||
template<class InPlaceFactory> explicit optional ( InPlaceFactory const& f ) ;
|
||||
template<InPlaceFactory> explicit optional ( InPlaceFactory const& f ) ;
|
||||
|
||||
template<class TypedInPlaceFactory> explicit optional ( TypedInPlaceFactory const& f ) ;
|
||||
template<TypedInPlaceFactory> explicit optional ( TypedInPlaceFactory const& f ) ;
|
||||
|
||||
optional& operator = ( none_t ) ;
|
||||
|
||||
@ -341,14 +343,14 @@ class optional
|
||||
|
||||
template<class U> optional& operator = ( optional<U> const& rhs ) ;
|
||||
|
||||
template<class InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ;
|
||||
template<InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ;
|
||||
|
||||
template<class TypedInPlaceFactory> optional& operator = ( TypedInPlaceFactory const& f ) ;
|
||||
template<TypedInPlaceFactory> optional& operator = ( TypedInPlaceFactory const& f ) ;
|
||||
|
||||
T const& get() const ;
|
||||
T& get() ;
|
||||
|
||||
T<span lang="es"> const&</span> get_value_or( T const& default ) const ; <u><i>[new in 1.34]</u></i>
|
||||
T const& get_value_or( T const& default ) const ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
T const* operator ->() const ;
|
||||
T* operator ->() ;
|
||||
@ -383,11 +385,59 @@ template<class T> inline bool operator <= ( optional<T> const& x, op
|
||||
|
||||
template<class T> inline bool operator >= ( optional<T> const& x, optional<T> const& y ) ;
|
||||
|
||||
template<class T> inline bool operator == ( optional<T> const& x, T const& n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator != ( optional<T> const& x, T const& n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator < ( optional<T> const& x, T const& n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator > ( optional<T> const& x, T const& n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator <= ( optional<T> const& x, T const& n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator >= ( optional<T> const& x, T const& n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator == ( T const& n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator != ( T const& n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator < ( T const& n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator > ( T const& n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator <= ( T const& n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator >= ( T const& n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator == ( optional<T> const& x, none_t n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator != ( optional<T> const& x, none_t n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator < ( optional<T> const& x, none_t n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator > ( optional<T> const& x, none_t n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator <= ( optional<T> const& x, none_t n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator >= ( optional<T> const& x, none_t n ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator == ( none_t n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator != ( none_t n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator < ( none_t n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator > ( none_t n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator <= ( none_t n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline bool operator >= ( none_t n, optional<T> const& y ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline optional<T> make_optional ( T const& v ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline optional<T> make_optional ( bool condition, T const& v ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline T <span lang="es">const& </span>get_<span lang="es">optional_</span>value_or ( optional<T> const& opt, T const& default ) ; <u><i>[new in 1.34]</u></i>
|
||||
template<class T> inline T const& get_optional_value_or ( optional<T> const& opt, T const& default ) ; <u><i>[new in 1.34]</u></i>
|
||||
|
||||
template<class T> inline T const& get ( optional<T> const& opt ) ;
|
||||
|
||||
@ -457,9 +507,11 @@ used as the parameter.</p>
|
||||
</blockquote>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>#include <boost/none.hpp></pre>
|
||||
<pre>optional<T> n(none) ;
|
||||
assert ( !n ) ;</pre>
|
||||
<pre>
|
||||
#include <boost/none.hpp>
|
||||
optional<int> n(boost::none) ;
|
||||
assert ( !n ) ;
|
||||
</pre>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
|
||||
@ -476,9 +528,11 @@ in that case, this constructor has no effect.
|
||||
</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>T v;
|
||||
<pre>
|
||||
T v;
|
||||
optional<T> opt(v);
|
||||
assert ( *opt == v ) ;</pre>
|
||||
assert ( *opt == v ) ;
|
||||
</pre>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
|
||||
@ -492,29 +546,32 @@ instance of an internal type wrapping the reference 'ref'.</p>
|
||||
<p><b>Throws:</b> Nothing.</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>T v;
|
||||
<pre>
|
||||
T v;
|
||||
T& vref = v ;
|
||||
optional<T&> opt(vref);
|
||||
assert ( *opt == v ) ;
|
||||
++ v ; // mutate referee
|
||||
assert (*opt == v); </pre>
|
||||
assert (*opt == v);
|
||||
</pre>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
|
||||
<HR>
|
||||
|
||||
<pre>optional<T <i>(not a ref)</i>>::optional( bool condition, T const& v ) ;
|
||||
optional<T&> <span lang="es"> </span>::optional( bool condition, T& <span lang="es"> </span> v ) ;
|
||||
optional<T&> ::optional( bool condition, T& v ) ;
|
||||
</pre>
|
||||
|
||||
<blockquote>
|
||||
<p>If <i>condition</i> is <code>true</code>, same as:</p>
|
||||
<pre>optional<T <i>(not a ref)</i>>::optional( T const& v )
|
||||
optional<T&><span lang="es"> </span>::optional( T&<span lang="es"> </span> v )
|
||||
optional<T&> ::optional( T& v )
|
||||
</pre>
|
||||
<p>otherwise, same as:</p>
|
||||
<pre>optional<T <i>(not a ref)</i>>::optional()
|
||||
optional<T&><span lang="es"> </span>::optional()
|
||||
<pre>
|
||||
optional<T <i>(not a ref)</i>>::optional()
|
||||
optional<T&> ::optional()
|
||||
</pre>
|
||||
</blockquote>
|
||||
|
||||
@ -533,7 +590,8 @@ in that case, this constructor has no effect.
|
||||
</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>optional<T> uninit ;
|
||||
<pre>
|
||||
optional<T> uninit ;
|
||||
assert (!uninit);
|
||||
|
||||
optional<T> uinit2 ( uninit ) ;
|
||||
@ -562,7 +620,8 @@ is uninitialized.</p>
|
||||
reefer to the same object<b> </b>(they alias).</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>optional<T&> uninit ;
|
||||
<pre>
|
||||
optional<T&> uninit ;
|
||||
assert (!uninit);
|
||||
|
||||
optional<T&> uinit2 ( uninit ) ;
|
||||
@ -605,7 +664,8 @@ in that case, this constructor has no effect.
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
|
||||
<pre>optional<double> x(123.4);
|
||||
<pre>
|
||||
optional<double> x(123.4);
|
||||
assert ( *x == 123.4 ) ;
|
||||
|
||||
optional<int> y(x) ;
|
||||
@ -633,7 +693,8 @@ in that case, this constructor has no effect.
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
|
||||
<pre>class C { C ( char, double, std::string ) ; } ;
|
||||
<pre>
|
||||
class C { C ( char, double, std::string ) ; } ;
|
||||
|
||||
C v('A',123.4,"hello");
|
||||
|
||||
@ -649,6 +710,27 @@ assert ( *y == v ) ;
|
||||
|
||||
<HR>
|
||||
|
||||
<pre>optional& optional<T</i>>::operator= ( none_t n ) ;</pre>
|
||||
<blockquote>
|
||||
<p><b>Effect:</b> Same as opeator=(optional const& rhs), when rhs is default-constructed (uninitialized).</p>
|
||||
<p><b>Postconditions:</b> <b>*this</b> is uninitialized</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>
|
||||
#include <boost/none.hpp>
|
||||
|
||||
optional<int> def ;
|
||||
optional<int> opt(123) ;
|
||||
|
||||
opt = boost::none ;
|
||||
|
||||
assert ( opt == def ) ;
|
||||
</pre>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
|
||||
<HR>
|
||||
|
||||
<pre>optional& optional<T <i>(not a ref)</i>>::operator= ( T const& rhs ) ;</pre>
|
||||
<blockquote>
|
||||
<p><b>Effect:</b> Assigns the value 'rhs' to an <b>optional</b>.</p>
|
||||
@ -664,7 +746,8 @@ uninitialized and T's <i>copy constructor</i> fails, <b>*this</b> is left
|
||||
properly uninitialized]</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>T x;
|
||||
<pre>
|
||||
T x;
|
||||
optional<T> def ;
|
||||
optional<T> opt(x) ;
|
||||
|
||||
@ -687,7 +770,8 @@ and it references the same object referenced by <b>rhs.</b></p>
|
||||
new object. See <A HREF="#refassign">here</a> for details on this behavior.</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>int a = 1 ;
|
||||
<pre>
|
||||
int a = 1 ;
|
||||
int b = 2 ;
|
||||
T& ra = a ;
|
||||
T& rb = b ;
|
||||
@ -817,7 +901,7 @@ assert ( *opt1 == static_cast<U>(v) ) ;
|
||||
<HR>
|
||||
<pre>void optional<T>::reset() ;</pre>
|
||||
<blockquote>
|
||||
<p><b>Deprecated: </b>Same as operator=( detail::none_t );</p>
|
||||
<p><b>Deprecated: </b>Same as operator=( none_t n);</p>
|
||||
</blockquote>
|
||||
|
||||
<HR>
|
||||
@ -852,32 +936,6 @@ assert ( *opt == w ) ;
|
||||
|
||||
<HR>
|
||||
|
||||
<pre>T const& optional<T <i>(not a ref)</i>>::get_value_or( T const& default) const ;
|
||||
T& optional<T <i>(not a ref)</i>>::get_value_or( T& default ) ;
|
||||
|
||||
inline T const& get_optional_value_or ( optional<T<i> (not a ref)</i>> const& o, T const& default ) ;
|
||||
inline T& get_optional_value_or ( optional<T <i>(not a ref)</i>>& o, T& default ) ;
|
||||
</pre>
|
||||
<blockquote>
|
||||
<p><b>Returns:</b> A reference to the contained value, if any, or <code>default</code></p>
|
||||
<p><b>Throws:</b> Nothing.</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>T v, z ;
|
||||
optional<T> def;
|
||||
T const& y = def.get_value_or(z);
|
||||
assert ( y == z ) ;
|
||||
|
||||
optional<T> opt ( v );
|
||||
T const& u = get_optional_value_or(opt,z);
|
||||
assert ( u == v ) ;
|
||||
assert ( u != z ) ;
|
||||
</pre>
|
||||
</blockquote>
|
||||
<pre></pre>
|
||||
</blockquote>
|
||||
<HR>
|
||||
|
||||
|
||||
<pre>T const& optional<T&>::operator*() const ;
|
||||
T & optional<T<i>&</i>>::operator*();</pre>
|
||||
@ -907,29 +965,66 @@ assert ( *opt == v ) ;</pre>
|
||||
|
||||
<HR>
|
||||
|
||||
<pre>T const* optional<T <i>(not a ref)</i>>::get_ptr() const ;
|
||||
T* optional<T <i>(not a ref)</i>>::get_ptr() ;
|
||||
<pre>T const& optional<T>::get_value_or( T const& default) const ;
|
||||
T& optional<T>::get_value_or( T& default ) ;
|
||||
|
||||
inline T const* get_pointer ( optional<T <i>(not a ref)</i>> const& ) ;
|
||||
inline T* get_pointer ( optional<T <i>(not a ref)</i>> &) ;
|
||||
inline T const& get_optional_value_or ( optional<T> const& o, T const& default ) ;
|
||||
inline T& get_optional_value_or ( optional<T>& o, T& default ) ;
|
||||
</pre>
|
||||
<blockquote>
|
||||
<p><b>Returns:</b> A reference to the contained value (which can be itself a reference), if any, or <code>default</code></p>
|
||||
<p><b>Throws:</b> Nothing.</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>T v, z ;
|
||||
optional<T> def;
|
||||
T const& y = def.get_value_or(z);
|
||||
assert ( y == z ) ;
|
||||
|
||||
optional<T> opt ( v );
|
||||
T const& u = get_optional_value_or(opt,z);
|
||||
assert ( u == v ) ;
|
||||
assert ( u != z ) ;
|
||||
</pre>
|
||||
</blockquote>
|
||||
<pre></pre>
|
||||
</blockquote>
|
||||
|
||||
<HR>
|
||||
|
||||
<pre>T const* optional<T>::get_ptr() const ;
|
||||
T* optional<T>::get_ptr() ;
|
||||
|
||||
inline T const* get_pointer ( optional<T> const& ) ;
|
||||
inline T* get_pointer ( optional<T> &) ;
|
||||
</pre>
|
||||
<blockquote>
|
||||
<p><b>Returns:</b> If <b>*this</b> is initialized, a pointer to the contained
|
||||
value; else 0 (<i>null</i>).
|
||||
</p>
|
||||
<p><b>Throws:</b> Nothing.</p>
|
||||
<p><b>Notes:</b> If T is a reference type, the pointer is to the referenced object</p>
|
||||
<p><b>Notes:</b> The contained value is permanently stored within *this, so
|
||||
you should not hold nor delete this pointer
|
||||
you should not hold nor delete this pointer.
|
||||
</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>T v;
|
||||
optional<T> opt(v);
|
||||
optional<T> const copt(v);
|
||||
T* p = opt.get_ptr() ;
|
||||
T const* cp = copt.get_ptr();
|
||||
<pre>int v=123;
|
||||
optional<int> opt(v);
|
||||
optional<int> const copt(v);
|
||||
int* p = opt.get_ptr() ;
|
||||
int const* cp = copt.get_ptr();
|
||||
assert ( p == get_pointer(opt) );
|
||||
assert ( cp == get_pointer(copt) ) ;
|
||||
|
||||
int& rv = v ;
|
||||
optional<int&> optr(rv);
|
||||
|
||||
*(optr.get_ptr()) = 456 ;
|
||||
|
||||
assert ( v == 456 );
|
||||
|
||||
|
||||
</pre>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
@ -938,13 +1033,14 @@ assert ( cp == get_pointer(copt) ) ;
|
||||
<HR>
|
||||
|
||||
|
||||
<pre>T const* optional<T <i>(not a ref)</i>>::operator ->() const ;
|
||||
T* optional<T <i>(not a ref)</i>>::operator ->() ;
|
||||
<pre>T const* optional<T>::operator ->() const ;
|
||||
T* optional<T>::operator ->() ;
|
||||
</pre>
|
||||
<blockquote>
|
||||
<p><b>Requirements: *this</b> is initialized.</p>
|
||||
<p><b>Returns:</b> A pointer to the contained value.</p>
|
||||
<p><b>Throws:</b> Nothing.</p>
|
||||
<p><b>Notes:</b> If T is a reference type, the pointer is to the referenced object</p>
|
||||
<p><b>Notes:</b> The requirement is asserted via BOOST_ASSERT().</p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
@ -952,6 +1048,14 @@ T* optional<T <i>(not a ref)</i>>::operator ->() ;
|
||||
X x ;
|
||||
optional<X> opt (x);
|
||||
opt->mdata = 2 ;
|
||||
|
||||
X& rx = x ;
|
||||
|
||||
optional<X&> optr (rx);
|
||||
optr->mdata = 4 ;
|
||||
|
||||
assert ( x.mdata = 4 )
|
||||
|
||||
</pre>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
@ -1154,13 +1258,50 @@ assert ( optX != optZ ) ;
|
||||
<p><b>Throws:</b> Nothing.</p>
|
||||
</blockquote>
|
||||
|
||||
<HR>
|
||||
<pre>
|
||||
bool operator == ( optional<T> const& x, T const& n );
|
||||
bool operator != ( optional<T> const& x, T const& n );
|
||||
bool operator < ( optional<T> const& x, T const& n );
|
||||
bool operator > ( optional<T> const& x, T const& n );
|
||||
bool operator <= ( optional<T> const& x, T const& n );
|
||||
bool operator >= ( optional<T> const& x, T const& n );
|
||||
bool operator == ( T const& n, optional<T> const& y );
|
||||
bool operator != ( T const& n, optional<T> const& y );
|
||||
bool operator < ( T const& n, optional<T> const& y );
|
||||
bool operator > ( T const& n, optional<T> const& y );
|
||||
bool operator <= ( T const& n, optional<T> const& y );
|
||||
bool operator >= ( T const& n, optional<T> const& y );
|
||||
</pre>
|
||||
<blockquote>
|
||||
<p><b>Returns:</b> The result obtained by replacing the argument 'n' by optional<T>(n).</p>
|
||||
</blockquote>
|
||||
|
||||
<HR>
|
||||
<pre>
|
||||
bool operator == ( optional<T> const& x, none_t n );
|
||||
bool operator != ( optional<T> const& x, none_t n );
|
||||
bool operator < ( optional<T> const& x, none_t n );
|
||||
bool operator > ( optional<T> const& x, none_t n );
|
||||
bool operator <= ( optional<T> const& x, none_t n );
|
||||
bool operator >= ( optional<T> const& x, none_t n );
|
||||
bool operator == ( none_t n, optional<T> const& y );
|
||||
bool operator != ( none_t n, optional<T> const& y );
|
||||
bool operator < ( none_t n, optional<T> const& y );
|
||||
bool operator > ( none_t n, optional<T> const& y );
|
||||
bool operator <= ( none_t n, optional<T> const& y );
|
||||
bool operator >= ( none_t n, optional<T> const& y );
|
||||
</pre>
|
||||
<blockquote>
|
||||
<p><b>Returns:</b> The result obtained by replacing the argument 'n' by optional<T>().</p>
|
||||
</blockquote>
|
||||
<HR>
|
||||
|
||||
<pre>void swap ( optional<T>& x, optional<T>& y );</pre>
|
||||
|
||||
<blockquote>
|
||||
<p><b>Effect:</b> If both <b>x</b> and <b>y</b> are initialized, calls <code>swap(*x,*y)</code> using std::swap.<br>
|
||||
If only one is initialized, say x, calls: <code>y.reset(*x); x.reset();</code><br>
|
||||
If only one is initialized, say x, calls: <code>y = *x; x = boost:none;</code><br>
|
||||
If none is initialized, does nothing. </p>
|
||||
<p><b>Postconditions:</b> The states of x and y interchanged.</p>
|
||||
<p><b>Throws:</b> If both are initialized, whatever swap(T&,T&) throws.
|
||||
@ -1169,7 +1310,7 @@ If only one is initialized, whatever T::T ( T const& ) throws. </p>
|
||||
If only one is initialized, T::~T() and T::T( T const& ) is called. </p>
|
||||
<p><b>Exception Safety:</b> If both are initialized, this operation has the exception
|
||||
safety guarantees of swap(T&,T&).<br>
|
||||
If only one is initialized, it has the same <b>basic</b> guarantee as optional<T>::reset( T const& ). </p>
|
||||
If only one is initialized, it has the same <b>basic</b> guarantee as optional<T>::operator=( T const& ). </p>
|
||||
<p><b>Example:</b></p>
|
||||
<blockquote>
|
||||
<pre>T x(12);
|
||||
@ -1219,12 +1360,12 @@ void receive_async_message()
|
||||
<pre>optional<string> name ;
|
||||
if ( database.open() )
|
||||
{
|
||||
name.reset ( database.lookup(employer_name) ) ;
|
||||
name = database.lookup(employer_name) ;
|
||||
}
|
||||
else
|
||||
{
|
||||
if ( can_ask_user )
|
||||
name.reset ( user.ask(employer_name) ) ;
|
||||
name = user.ask(employer_name) ;
|
||||
}
|
||||
|
||||
if ( name )
|
||||
@ -1245,7 +1386,7 @@ else print("employer's name not found!");
|
||||
void clip_in_rect ( rect const& rect )
|
||||
{
|
||||
....
|
||||
m_clipping_rect.reset ( rect ) ; // initialized here.
|
||||
m_clipping_rect = rect ; // initialized here.
|
||||
}
|
||||
|
||||
void draw ( canvas& cvs )
|
||||
@ -1289,16 +1430,17 @@ some operations are not available in this case:</p>
|
||||
<li>Converting assignment</li>
|
||||
<li>InPlace construction</li>
|
||||
<li>InPlace assignment</li>
|
||||
<li>Value-access via pointer</li>
|
||||
</ul>
|
||||
<p>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: </p>
|
||||
value, a true real reference is stored, thus aliasing can ocurr: </p>
|
||||
|
||||
<ul>
|
||||
<li>Copies of optional<T&> will copy the references but all these references
|
||||
<li>Copies of optional<T&> copies the reference, but all copied references
|
||||
will nonetheless reefer to the same object.</li>
|
||||
<li>Value-access will actually provide access to the referenced object rather
|
||||
<li>Value-access provides access to the referenced object rather
|
||||
than the reference itself.</li>
|
||||
<li>Pointer-access provides a pointer to the referenced object rather
|
||||
than a pointer to the reference itself.</li>
|
||||
</ul>
|
||||
|
||||
<HR>
|
||||
@ -1309,7 +1451,7 @@ Clearly, there is no other choice.</p>
|
||||
<pre>int x = 1 ;
|
||||
int& rx = x ;
|
||||
optional<int&> ora ;
|
||||
optional<int&> orb(x) ;
|
||||
optional<int&> orb(rx) ;
|
||||
ora = orb ; // now 'ora' is bound to 'x' through 'rx'
|
||||
*ora = 2 ; // Changes value of 'x' through 'ora'
|
||||
assert(x==2);
|
||||
@ -1320,7 +1462,7 @@ referenced object; it's value changes but the reference is never rebound.</p>
|
||||
int& ra = a ;
|
||||
int b = 2 ;
|
||||
int& rb = b ;
|
||||
ra = rb ; // Changes the value of 'a' to 'b'
|
||||
ra = rb ; // Changes the VALUE of 'a' to that of 'b'
|
||||
assert(a==b);
|
||||
b = 3 ;
|
||||
assert(ra!=b); // 'ra' is not rebound to 'b'
|
||||
@ -1346,38 +1488,68 @@ C++ references.<br>
|
||||
It is true that optional<U> strives to behave as much as possible as U does
|
||||
whenever it is initialized; but in the case when U is T&, doing so would result
|
||||
in inconsistent behavior w.r.t to the lvalue initialization state.</p>
|
||||
<p>Imagine optional<T&> forwarding assignment to the referenced object (thus
|
||||
changing the referenced object value but not rebinding), and consider the
|
||||
following code :</p>
|
||||
<pre> optional<int&> a = get();
|
||||
int x = 1 ;
|
||||
int& rx = x ;
|
||||
optional<int&> b(rx);
|
||||
a = b ;
|
||||
<p>Consider the following code :</p>
|
||||
<pre>
|
||||
int x = 1 ;
|
||||
int& rx = x ;
|
||||
void foo ( optional<int&> & outer )
|
||||
{
|
||||
optional<int&> b(rx);
|
||||
outer = b ;
|
||||
}
|
||||
</pre>
|
||||
<p>What should the assignment to 'outer' do?<br>
|
||||
If 'outer' is <i>uninitialized</i>, the answer is clear: it should bind to 'x' (so we now have
|
||||
a second reference to 'x').<br>
|
||||
But what if 'outer' is already <i>initialized?</i><br>
|
||||
The assignment could change the value of the
|
||||
referenced object (whatever that is), but doing that would be inconsistent with the uninitialized case
|
||||
and then you wouldn't be able to reason at compile time about all the references to x since
|
||||
the appearance of a new reference to it would depend on wheter the lvalue ('outer')
|
||||
is initialized or not.</p>
|
||||
<p>Arguably, if rebinding the reference to another object is wrong for your code, then is
|
||||
likely that binding it for the fist time via assignment instead of intialization is also wrong.
|
||||
In that case, you can always just assign the value to the referenced object directly via
|
||||
the access operator <code>*opt=value</code>.</p>
|
||||
<p>If rebinding is wrong but first-time binding
|
||||
isn't (via assignment), you can always work around the rebinding semantics using a discriminator:</p>
|
||||
<pre>
|
||||
if ( !opt )
|
||||
opt = value ; // first-time binding
|
||||
else *opt = value ; // assign to referee without rebinding
|
||||
</pre>
|
||||
|
||||
<HR>
|
||||
|
||||
<H2><A NAME="none">none_t and none</A></H2>
|
||||
<p>optional<T> supports uninitialized states with a convenient syntax via a constant of
|
||||
the <i>implementation-defined</i> type <code>boost::none_t</code>, identified as <code>boost::none</code>.</p>
|
||||
<p>Starting with Boost version 1.34.0, both <code>boost::none_t</code> and <code>boost::none</code> are
|
||||
included in <code>boost/none.hpp</code>, which is automatically included by <code>boost/optional/optional.hpp</code>
|
||||
</p>
|
||||
<p>This contant is similar in purpose to NULL, except that is not a <i>null pointer value</i>. You can use it to initialize
|
||||
an optional<T> instance, which has the same effect of a default constructor, and you can assign it which has the
|
||||
effect of reseting the optional<T> instance. You can also use it in relational operators to make the predicate expression
|
||||
more clear.</p>
|
||||
<p>Here are some typical examples:</p>
|
||||
<pre>
|
||||
#include "boost/optional/optional.hpp" // boost/none.hpp is included automatically
|
||||
|
||||
boost::optional<int> foo ( int a )
|
||||
{
|
||||
return some_condition(a) ? boost::make_optional(a) : boost::none ;
|
||||
|
||||
// NOTE: in real code you can just use this: make_optional(some_condition(a), a )
|
||||
}
|
||||
|
||||
boost::optional<int> opt = boost::none ;
|
||||
|
||||
if ( opt == boost::none )
|
||||
opt = foo(123);
|
||||
|
||||
opt = boost::none ;
|
||||
|
||||
</pre>
|
||||
<p>What does the assignment do?<br>
|
||||
If 'a' is <i>uninitialized</i>, the answer is clear: it binds to 'x' (we now have
|
||||
another reference to 'x').<br>
|
||||
But what if 'a' is already <i>initialized? </i>it would change the value of the
|
||||
referenced object (whatever that is); which is inconsistent with the other
|
||||
possible case.</p>
|
||||
<p>If optional<T&> would assign just like T& does, you would never be able to
|
||||
use Optional's assignment without explicitly handling the previous
|
||||
initialization state unless your code is capable of functioning whether after
|
||||
the assignment, 'a'
|
||||
aliases the same object as 'b' or not.</p>
|
||||
<p>That is, you would have to discriminate in order to be consistency.<br>
|
||||
<br>
|
||||
If in your code rebinding to another object is not an option, then is very
|
||||
likely that binding for the fist time isn't either. In such case, assignment to
|
||||
an <i>uninitialized</i> optional<T&> shall be prohibited. It is quite
|
||||
possible that in such scenario the precondition that the lvalue must be already
|
||||
initialized exist. If it doesn't, then binding for the first time is OK while
|
||||
rebinding is not which is IMO
|
||||
very unlikely.<br>
|
||||
In such scenario, you can assign the value itself directly, as in:</p>
|
||||
<pre>assert(!!opt);
|
||||
*opt=value; </pre>
|
||||
|
||||
<HR>
|
||||
|
||||
@ -1506,9 +1678,8 @@ public:
|
||||
the <i>maybe</i> state <u>represents a valid value</u>, unlike the corresponding state
|
||||
of an uninitialized optional<bool>.<br>
|
||||
It should be carefully considered if an optional<bool> instead of a tribool is really needed</p>
|
||||
<p>Second, optional<> provides an implicit conversion to bool. This conversion
|
||||
refers to the initialization state and not to the contained value.<br>
|
||||
Using optional<bool> can lead to subtle errors due to the implicit bool conversion:</p>
|
||||
<p>Second, optional<> provides a simple way to test initialization state: an implicit conversion to a type that evaluates as a 'bool' in a boolean context.<br>
|
||||
Using optional<bool> can lead to subtle errors due to this implicit conversion:</p>
|
||||
<pre>void foo ( bool v ) ;
|
||||
void bar()
|
||||
{
|
||||
@ -1524,7 +1695,9 @@ void bar()
|
||||
integral promotions don't apply (i.e. if foo() takes an 'int' instead, it won't compile). <HR>
|
||||
|
||||
<H2><A NAME="exsafety">Exception Safety Guarantees</A></H2>
|
||||
<H3><u>Assignment and Reset:</u></H3>
|
||||
|
||||
<H3><u>Assignment:</u></H3>
|
||||
<p><i>IMPORTANT NOTE: This changed in 1.33.1 with respect to previous versions</i></p>
|
||||
<p>Because of the current implementation (see <A HREF="#impl">Implementation Notes</A>), all
|
||||
of the assignment methods:</p>
|
||||
<ul>
|
||||
@ -1537,60 +1710,17 @@ of the assignment methods:</p>
|
||||
InPlaceFactory const& ) </code></li>
|
||||
<li> <code>template<class TypedInPlaceFactory> optional<T>::operator= (
|
||||
TypedInPlaceFactory const& ) </code></li>
|
||||
<li> <code>optional<T>:::reset ( T const&)</code></li>
|
||||
</ul>
|
||||
<p>Can only <i>guarantee</i> the <u>basic exception safety</u>: The lvalue optional is left <u>uninitialized</u> if an exception is thrown (any previous value is <i>first</i> destroyed using T::~T())</p>
|
||||
<p>cannot offer any <i>exception safety guarantee</i> beyond that provided by <code>T::operator=( T const& )</code></p>
|
||||
<p>On the other hand, the <i>uninitializing</i> methods:</p>
|
||||
<ul>
|
||||
<li><code>optional<T>::operator= ( detail::none_t ) </code></li>
|
||||
<li><code>optional<T>::reset()</code></li>
|
||||
</ul>
|
||||
<p>Provide the no-throw guarantee (assuming a no-throw T::~T())</p>
|
||||
<p>However, since <code>optional<></code> 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.</p>
|
||||
<pre>//
|
||||
// Case 1: Exception thrown during assignment.
|
||||
//
|
||||
T v0(123);
|
||||
optional<T> opt0(v0);
|
||||
try
|
||||
{
|
||||
T v1(456);
|
||||
optional<T> opt1(v1);
|
||||
opt0 = opt1 ;
|
||||
<p>Provides the no-throw guarantee (assuming a no-throw T::~T()) becuse it only destroys the stored object.</p>
|
||||
|
||||
// If no exception was thrown, assignment succeeded.
|
||||
assert( *opt0 == v1 ) ;
|
||||
}
|
||||
catch(...)
|
||||
{
|
||||
// If any exception was thrown, 'opt0' is reset to uninitialized.
|
||||
assert( !opt0 ) ;
|
||||
}
|
||||
|
||||
//
|
||||
// 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 ) ;
|
||||
}
|
||||
</pre>
|
||||
<H3><u>Swap:</u></H3>
|
||||
<p><code>void swap( optional<T>&, optional<T>& )</code> has the same exception guarantee as <code>swap(T&,T&)</code> when both optionals are initialized.<br>
|
||||
If only one of the optionals is initialized, it gives the same <i>basic</i> exception guarantee as <code>optional<T>::reset( T const& )</code> (since <code>optional<T>::reset()</code> doesn't throw).<br>
|
||||
If only one of the optionals is initialized, it gives the same exception guarantee as <code>T::operator=( T const& )</code> (since <code>optional<T>::operator=( none_t )</code> doesn't throw).<br>
|
||||
If none of the optionals is initialized, it has no-throw guarantee since it is a no-op. </p>
|
||||
|
||||
<HR>
|
||||
@ -1604,14 +1734,11 @@ T <u>is not</u> required to be <a href="http://www.sgi.com/tech/stl/DefaultConst
|
||||
|
||||
<H2><A NAME="impl">Implementation Notes</A></H2>
|
||||
<p>optional<T> is currently implemented
|
||||
using a custom aligned storage facility built from <code>alignment_of</code> and <code>type_with_alignment</code> (both from Type Traits).
|
||||
It uses a separate boolean flag to indicate the initialization state.<br>
|
||||
Placement new with T's copy constructor and T's destructor
|
||||
are explicitly used to initialize,copy and destroy optional values.<br>
|
||||
As a result, T's default constructor is effectively by-passed, but the exception
|
||||
guarantees are basic.<br>
|
||||
It is planned to replace the current implementation with another with
|
||||
stronger exception safety, such as a future boost::variant<T,nil_t>. </p>
|
||||
using a custom aligned storage facility built from <code>alignment_of</code> and <code>type_with_alignment</code> (both from Type Traits).
|
||||
It uses a separate boolean flag to indicate the initialization state.</p>
|
||||
<p>Placement new with T's copy constructor and T's destructor
|
||||
is explicitly used to initialize and destroy optional values. This allows T's default constructor to be effectively by-passed.</p>
|
||||
<p>If assignment is used and the lvalue optional is uninitialized, T's copy constructor is used. However, if it is already initialized, T's assignment operator is used. This prevents optional from offering any exception guarantee stronger than the one offered by the type T itself</p>
|
||||
|
||||
<HR>
|
||||
|
||||
@ -1665,12 +1792,12 @@ T <u>is not</u> required to be <a href="http://www.sgi.com/tech/stl/DefaultConst
|
||||
</blockquote>
|
||||
<HR>
|
||||
|
||||
<P>Revised April 21, 2005</P>
|
||||
<p><EFBFBD> Copyright Fernando Luis Cacciola Carballal, 2003,2004,2005</p>
|
||||
<P>Revised March 27, 2007</P>
|
||||
<p><EFBFBD> Copyright Fernando Luis Cacciola Carballal, 2003-2007</p>
|
||||
<p> Use, modification, and distribution are subject to the Boost Software
|
||||
License, Version 1.0. (See accompanying file <a href="../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</p>
|
||||
<P>Developed by <A HREF="mailto:fernando_cacciola@hotmail.com">Fernando Cacciola</A>,
|
||||
the latest version of this file can be found at <A
|
||||
HREF="http://www.boost.org">www.boost.org</A>, and the boost <A HREF="http://www.boost.org/more/mailing_lists.htm#main">discussion lists</A></P>
|
||||
</pre></BODY>
|
||||
</HTML>
|
||||
</HTML>
|
||||
@ -22,7 +22,7 @@ Distributed under the Boost Software License, Version 1.0.
|
||||
[/ Cited Boost resources ]
|
||||
|
||||
[def __BOOST_VARIANT__ [@../../../variant/index.html Boost.Variant]]
|
||||
[def __BOOST_TRIBOOL__ [@../../../../doc/html/tribool.html boost::tribool]]
|
||||
[def __BOOST_TRIBOOL__ [@../../../tribool/index.html boost::tribool]]
|
||||
|
||||
[def __OPTIONAL_POINTEE__ [@../../../utility/OptionalPointee.html OptionalPointee]]
|
||||
[def __COPY_CONSTRUCTIBLE__ [@../../../utility/CopyConstructible.html Copy Constructible]]
|
||||
@ -40,6 +40,11 @@ Distributed under the Boost Software License, Version 1.0.
|
||||
|
||||
[/ Icons ]
|
||||
|
||||
[def __NOTE__ [$images/note.png]]
|
||||
[def __ALERT__ [$images/caution.png]]
|
||||
[def __DETAIL__ [$images/note.png]]
|
||||
[def __TIP__ [$images/tip.png]]
|
||||
[def __QUESTION_MARK__ [$images/question.png]]
|
||||
[def __SPACE__ [$images/space.png]]
|
||||
[def __GO_TO__ [$images/callouts/R.png]]
|
||||
|
||||
|
||||
@ -126,7 +126,6 @@
|
||||
Because `T` might be of reference type, in the sequel, those entries whose
|
||||
semantic depends on `T` being of reference type or not will be distinguished
|
||||
using the following convention:
|
||||
|
||||
* If the entry reads: `optional<T`['(not a ref)]`>`, the description
|
||||
corresponds only to the case where `T` is not of reference type.
|
||||
* If the entry reads: `optional<T&>`, the description corresponds only to
|
||||
|
||||
@ -4,7 +4,7 @@
|
||||
// (See accompanying file LICENSE_1_0.txt or copy at
|
||||
// http://www.boost.org/LICENSE_1_0.txt)
|
||||
//
|
||||
// See http://www.boost.org/libs/optional for documentation.
|
||||
// See http://www.boost.org/lib/optional/ for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// fernando_cacciola@hotmail.com
|
||||
|
||||
@ -4,7 +4,7 @@
|
||||
// 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/libs/optional for documentation.
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// fernando_cacciola@hotmail.com
|
||||
|
||||
@ -4,7 +4,7 @@
|
||||
// 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/libs/optional for documentation.
|
||||
// See http://www.boost.org/lib/optional for documentation.
|
||||
//
|
||||
// You are welcome to contact the author at:
|
||||
// fernando_cacciola@hotmail.com
|
||||
|
||||
@ -1,13 +1,13 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="refresh" content="0; URL=doc/html/index.html">
|
||||
<meta http-equiv="refresh" content="0; URL=doc/optional.html">
|
||||
</head>
|
||||
<body>
|
||||
Automatic redirection failed, please go to
|
||||
<a href="doc/html/index.html">doc/html/index.html</a>. <hr>
|
||||
<p><EFBFBD> Copyright Beman Dawes, 2001</p>
|
||||
<a href="doc/optional.html">doc/optional.html</a>. <hr>
|
||||
<p><EFBFBD> Copyright Beman Dawes, 2001</p>
|
||||
<p>Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||||
file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or copy
|
||||
at <a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</p>
|
||||
</body>
|
||||
</html>
|
||||
</html>
|
||||
@ -1,23 +0,0 @@
|
||||
// Copyright (C) 2003, Fernando Luis Cacciola Carballal.
|
||||
//
|
||||
// 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:
|
||||
// fernando_cacciola@hotmail.com
|
||||
//
|
||||
#include "boost/optional.hpp"
|
||||
|
||||
//
|
||||
// THIS TEST SHOULD FAIL TO COMPILE
|
||||
//
|
||||
void optional_reference__test_no_ptr_access()
|
||||
{
|
||||
boost::optional<int&> opt ;
|
||||
opt.get_ptr();
|
||||
}
|
||||
|
||||
|
||||
Reference in New Issue
Block a user