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<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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<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
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<meta name="ProgId" content="FrontPage.Editor.Document">
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<title>C++ Type traits</title>
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</head>
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<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
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<h2 align="center">C++ Type traits</h2>
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<p align="center"><em>by John Maddock and Steve Cleary</em></p>
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<p align="center"><em>This is a draft of an article that will appear in a future
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issue of </em><a href="http://www.ddj.com"><em>Dr Dobb's Journal</em></a></p>
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<p>Generic programming (writing code which works with any data type meeting a
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set of requirements) has become the method of choice for providing reusable
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code. However, there are times in generic programming when "generic"
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just isn't good enough - sometimes the differences between types are too large
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for an efficient generic implementation. This is when the traits technique
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becomes important - by encapsulating those properties that need to be considered
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on a type by type basis inside a traits class, we can minimise the amount of
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code that has to differ from one type to another, and maximise the amount of
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generic code.</p>
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<p>Consider an example: when working with character strings, one common
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operation is to determine the length of a null terminated string. Clearly it's
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possible to write generic code that can do this, but it turns out that there are
|
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much more efficient methods available: for example, the C library functions <font size="2" face="Courier New">strlen</font>
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and <font size="2" face="Courier New">wcslen</font> are usually written in
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assembler, and with suitable hardware support can be considerably faster than a
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generic version written in C++. The authors of the C++ standard library realised
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this, and abstracted the properties of <font size="2" face="Courier New">char</font>
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and <font size="2" face="Courier New">wchar_t</font> into the class <font size="2" face="Courier New">char_traits</font>.
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Generic code that works with character strings can simply use <font size="2" face="Courier New">char_traits<>::length</font>
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to determine the length of a null terminated string, safe in the knowledge that
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specialisations of <font size="2" face="Courier New">char_traits</font> will use
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the most appropriate method available to them.</p>
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<h4>Type traits</h4>
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<p>Class <font size="2" face="Courier New">char_traits</font> is a classic
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example of a collection of type specific properties wrapped up in a single class
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- what Nathan Myers termed a <i>baggage class</i>[1]. In the Boost type-traits
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library, we[2] have written a set of very specific traits classes, each of which
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encapsulate a single trait from the C++ type system; for example, is a type a
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pointer or a reference type? Or does a type have a trivial constructor, or a
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const-qualifier? The type-traits classes share a unified design: each class has
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a single member <i>value</i>, a compile-time constant that is true if the type
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has the specified property, and false otherwise. As we will show, these classes
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can be used in generic programming to determine the properties of a given type
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and introduce optimisations that are appropriate for that case.</p>
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<p>The type-traits library also contains a set of classes that perform a
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specific transformation on a type; for example, they can remove a top-level
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const or volatile qualifier from a type. Each class that performs a
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transformation defines a single typedef-member <i>type</i> that is the result of
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the transformation. All of the type-traits classes are defined inside namespace <font size="2" face="Courier New">boost</font>;
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for brevity, namespace-qualification is omitted in most of the code samples
|
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given.</p>
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<h4>Implementation</h4>
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<p>There are far too many separate classes contained in the type-traits library
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to give a full implementation here - see the source code in the Boost library
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for the full details - however, most of the implementation is fairly repetitive
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anyway, so here we will just give you a flavour for how some of the classes are
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implemented. Beginning with possibly the simplest class in the library, is_void<T>
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has a member <i>value</i> that is true only if T is void.</p>
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<pre>template <typename T>
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struct is_void
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{ static const bool value = false; };
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template <>
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struct is_void<void>
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{ static const bool value = true; };</pre>
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<p>Here we define a primary version of the template class <font size="2" face="Courier New">is_void</font>,
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and provide a full-specialisation when T is void. While full specialisation of a
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template class is an important technique, sometimes we need a solution that is
|
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halfway between a fully generic solution, and a full specialisation. This is
|
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exactly the situation for which the standards committee defined partial
|
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template-class specialisation. As an example, consider the class
|
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boost::is_pointer<T>: here we needed a primary version that handles all
|
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the cases where T is not a pointer, and a partial specialisation to handle all
|
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the cases where T is a pointer:</p>
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<pre>template <typename T>
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struct is_pointer
|
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{ static const bool value = false; };
|
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|
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template <typename T>
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struct is_pointer<T*>
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{ static const bool value = true; };</pre>
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<p>The syntax for partial specialisation is somewhat arcane and could easily
|
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occupy an article in its own right; like full specialisation, in order to write
|
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a partial specialisation for a class, you must first declare the primary
|
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template. The partial specialisation contains an extra <<EFBFBD>> after the
|
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class name that contains the partial specialisation parameters; these define the
|
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types that will bind to that partial specialisation rather than the default
|
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template. The rules for what can appear in a partial specialisation are somewhat
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convoluted, but as a rule of thumb if you can legally write two function
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overloads of the form:</p>
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<pre>void foo(T);
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void foo(U);</pre>
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<p>Then you can also write a partial specialisation of the form:</p>
|
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<pre>template <typename T>
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class c{ /*details*/ };
|
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|
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template <typename T>
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|
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class c<U>{ /*details*/ };</pre>
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<p>This rule is by no means foolproof, but it is reasonably simple to remember
|
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and close enough to the actual rule to be useful for everyday use.</p>
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<p>As a more complex example of partial specialisation consider the class
|
||||
remove_bounds<T>. This class defines a single typedef-member <i>type</i>
|
||||
that is the same type as T but with any top-level array bounds removed; this is
|
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an example of a traits class that performs a transformation on a type:</p>
|
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<pre>template <typename T>
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struct remove_bounds
|
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{ typedef T type; };
|
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|
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template <typename T, std::size_t N>
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struct remove_bounds<T[N]>
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{ typedef T type; };</pre>
|
||||
<p>The aim of remove_bounds is this: imagine a generic algorithm that is passed
|
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an array type as a template parameter, <font size="2" face="Courier New">remove_bounds</font>
|
||||
provides a means of determining the underlying type of the array. For example <code>remove_bounds<int[4][5]>::type</code>
|
||||
would evaluate to the type <code>int[5]</code>. This example also shows that the
|
||||
number of template parameters in a partial specialisation does not have to match
|
||||
the number in the default template. However, the number of parameters that
|
||||
appear after the class name do have to match the number and type of the
|
||||
parameters in the default template.</p>
|
||||
<h4>Optimised copy</h4>
|
||||
<p>As an example of how the type traits classes can be used, consider the
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||||
standard library algorithm copy:</p>
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||||
<pre>template<typename Iter1, typename Iter2>
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||||
Iter2 copy(Iter1 first, Iter1 last, Iter2 out);</pre>
|
||||
<p>Obviously, there's no problem writing a generic version of copy that works
|
||||
for all iterator types Iter1 and Iter2; however, there are some circumstances
|
||||
when the copy operation can best be performed by a call to <font size="2" face="Courier New">memcpy</font>.
|
||||
In order to implement copy in terms of <font size="2" face="Courier New">memcpy</font>
|
||||
all of the following conditions need to be met:</p>
|
||||
<ul>
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||||
<li>Both of the iterator types Iter1 and Iter2 must be pointers.</li>
|
||||
<li>Both Iter1 and Iter2 must point to the same type - excluding <font size="2" face="Courier New">const</font>
|
||||
and <font size="2" face="Courier New">volatile</font>-qualifiers.</li>
|
||||
<li>The type pointed to by Iter1 must have a trivial assignment operator.</li>
|
||||
</ul>
|
||||
<p>By trivial assignment operator we mean that the type is either a scalar
|
||||
type[3] or:</p>
|
||||
<ul>
|
||||
<li>The type has no user defined assignment operator.</li>
|
||||
<li>The type does not have any data members that are references.</li>
|
||||
<li>All base classes, and all data member objects must have trivial assignment
|
||||
operators.</li>
|
||||
</ul>
|
||||
<p>If all these conditions are met then a type can be copied using <font size="2" face="Courier New">memcpy</font>
|
||||
rather than using a compiler generated assignment operator. The type-traits
|
||||
library provides a class <i>has_trivial_assign</i>, such that <code>has_trivial_assign<T>::value</code>
|
||||
is true only if T has a trivial assignment operator. This class "just
|
||||
works" for scalar types, but has to be explicitly specialised for
|
||||
class/struct types that also happen to have a trivial assignment operator. In
|
||||
other words if <i>has_trivial_assign</i> gives the wrong answer, it will give
|
||||
the "safe" wrong answer - that trivial assignment is not allowable.</p>
|
||||
<p>The code for an optimised version of copy that uses <font size="2" face="Courier New">memcpy</font>
|
||||
where appropriate is given in listing 1. The code begins by defining a template
|
||||
class <i>copier</i>, that takes a single Boolean template parameter, and has a
|
||||
static template member function <font size="2" face="Courier New">do_copy</font>
|
||||
which performs the generic version of <font size="2">copy</font> (in other words
|
||||
the "slow but safe version"). Following that there is a specialisation
|
||||
for <i>copier<true></i>: again this defines a static template member
|
||||
function <font size="2" face="Courier New">do_copy</font>, but this version uses
|
||||
memcpy to perform an "optimised" copy.</p>
|
||||
<p>In order to complete the implementation, what we need now is a version of
|
||||
copy, that calls <code>copier<true>::do_copy</code> if it is safe to use <font size="2" face="Courier New">memcpy</font>,
|
||||
and otherwise calls <code>copier<false>::do_copy</code> to do a
|
||||
"generic" copy. This is what the version in listing 1 does. To
|
||||
understand how the code works look at the code for <font size="2" face="Courier New">copy</font>
|
||||
and consider first the two typedefs <i>v1_t</i> and <i>v2_t</i>. These use <code>std::iterator_traits<Iter1>::value_type</code>
|
||||
to determine what type the two iterators point to, and then feed the result into
|
||||
another type-traits class <i>remove_cv</i> that removes the top-level
|
||||
const-volatile-qualifiers: this will allow copy to compare the two types without
|
||||
regard to const- or volatile-qualifiers. Next, <font size="2" face="Courier New">copy</font>
|
||||
declares an enumerated value <i>can_opt</i> that will become the template
|
||||
parameter to copier - declaring this here as a constant is really just a
|
||||
convenience - the value could be passed directly to class <font size="2" face="Courier New">copier</font>.
|
||||
The value of <i>can_opt</i> is computed by verifying that all of the following
|
||||
are true:</p>
|
||||
<ul>
|
||||
<li>first that the two iterators point to the same type by using a type-traits
|
||||
class <i>is_same</i>.</li>
|
||||
<li>Then that both iterators are real pointers - using the class <i>is_pointer</i>
|
||||
described above.</li>
|
||||
<li>Finally that the pointed-to types have a trivial assignment operator using
|
||||
<i>has_trivial_assign</i>.</li>
|
||||
</ul>
|
||||
<p>Finally we can use the value of <i>can_opt</i> as the template argument to
|
||||
copier - this version of copy will now adapt to whatever parameters are passed
|
||||
to it, if its possible to use <font size="2" face="Courier New">memcpy</font>,
|
||||
then it will do so, otherwise it will use a generic copy.</p>
|
||||
<h4>Was it worth it?</h4>
|
||||
<p>It has often been repeated in these columns that "premature optimisation
|
||||
is the root of all evil" [4]. So the question must be asked: was our
|
||||
optimisation premature? To put this in perspective the timings for our version
|
||||
of copy compared a conventional generic copy[5] are shown in table 1.</p>
|
||||
<p>Clearly the optimisation makes a difference in this case; but, to be fair,
|
||||
the timings are loaded to exclude cache miss effects - without this accurate
|
||||
comparison between algorithms becomes difficult. However, perhaps we can add a
|
||||
couple of caveats to the premature optimisation rule:</p>
|
||||
<ul>
|
||||
<li>If you use the right algorithm for the job in the first place then
|
||||
optimisation will not be required; in some cases, <font size="2" face="Courier New">memcpy</font>
|
||||
is the right algorithm.</li>
|
||||
<li>If a component is going to be reused in many places by many people then
|
||||
optimisations may well be worthwhile where they would not be so for a single
|
||||
case - in other words, the likelihood that the optimisation will be
|
||||
absolutely necessary somewhere, sometime is that much higher. Just as
|
||||
importantly the perceived value of the stock implementation will be higher:
|
||||
there is no point standardising an algorithm if users reject it on the
|
||||
grounds that there are better, more heavily optimised versions available.</li>
|
||||
</ul>
|
||||
<h4>Table 1: Time taken to copy 1000 elements using copy<const T*, T*>
|
||||
(times in micro-seconds)</h4>
|
||||
<table border="1" cellpadding="7" cellspacing="1" width="529">
|
||||
<tr>
|
||||
<td valign="top" width="33%">
|
||||
<p align="center">Version</p>
|
||||
</td>
|
||||
<td valign="top" width="33%">
|
||||
<p align="center">T</p>
|
||||
</td>
|
||||
<td valign="top" width="33%">
|
||||
<p align="center">Time</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="33%">"Optimised" copy</td>
|
||||
<td valign="top" width="33%">char</td>
|
||||
<td valign="top" width="33%">0.99</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="33%">Conventional copy</td>
|
||||
<td valign="top" width="33%">char</td>
|
||||
<td valign="top" width="33%">8.07</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="33%">"Optimised" copy</td>
|
||||
<td valign="top" width="33%">int</td>
|
||||
<td valign="top" width="33%">2.52</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="33%">Conventional copy</td>
|
||||
<td valign="top" width="33%">int</td>
|
||||
<td valign="top" width="33%">8.02</td>
|
||||
</tr>
|
||||
</table>
|
||||
<p> </p>
|
||||
<h4>Pair of References</h4>
|
||||
<p>The optimised copy example shows how type traits may be used to perform
|
||||
optimisation decisions at compile-time. Another important usage of type traits
|
||||
is to allow code to compile that otherwise would not do so unless excessive
|
||||
partial specialization is used. This is possible by delegating partial
|
||||
specialization to the type traits classes. Our example for this form of usage is
|
||||
a pair that can hold references [6].</p>
|
||||
<p>First, let us examine the definition of "std::pair", omitting the
|
||||
comparision operators, default constructor, and template copy constructor for
|
||||
simplicity:</p>
|
||||
<pre>template <typename T1, typename T2>
|
||||
struct pair
|
||||
{
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
|
||||
T1 first;
|
||||
T2 second;
|
||||
|
||||
pair(const T1 & nfirst, const T2 & nsecond)
|
||||
:first(nfirst), second(nsecond) { }
|
||||
};</pre>
|
||||
<p>Now, this "pair" cannot hold references as it currently stands,
|
||||
because the constructor would require taking a reference to a reference, which
|
||||
is currently illegal [7]. Let us consider what the constructor's parameters
|
||||
would have to be in order to allow "pair" to hold non-reference types,
|
||||
references, and constant references:</p>
|
||||
<table border="1" cellpadding="7" cellspacing="1" width="638">
|
||||
<tr>
|
||||
<td valign="top" width="50%">Type of "T1"</td>
|
||||
<td valign="top" width="50%">Type of parameter to initializing constructor</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="50%">
|
||||
<pre>T</pre>
|
||||
</td>
|
||||
<td valign="top" width="50%">
|
||||
<pre>const T &</pre>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="50%">
|
||||
<pre>T &</pre>
|
||||
</td>
|
||||
<td valign="top" width="50%">
|
||||
<pre>T &</pre>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="50%">
|
||||
<pre>const T &</pre>
|
||||
</td>
|
||||
<td valign="top" width="50%">
|
||||
<pre>const T &</pre>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>A little familiarity with the type traits classes allows us to construct a
|
||||
single mapping that allows us to determine the type of parameter from the type
|
||||
of the contained class. The type traits classes provide a transformation "add_reference",
|
||||
which adds a reference to its type, unless it is already a reference.</p>
|
||||
<table border="1" cellpadding="7" cellspacing="1" width="580">
|
||||
<tr>
|
||||
<td valign="top" width="21%">Type of "T1"</td>
|
||||
<td valign="top" width="27%">Type of "const T1"</td>
|
||||
<td valign="top" width="53%">Type of "add_reference<const
|
||||
T1>::type"</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="21%">
|
||||
<pre>T</pre>
|
||||
</td>
|
||||
<td valign="top" width="27%">
|
||||
<pre>const T</pre>
|
||||
</td>
|
||||
<td valign="top" width="53%">
|
||||
<pre>const T &</pre>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="21%">
|
||||
<pre>T &</pre>
|
||||
</td>
|
||||
<td valign="top" width="27%">
|
||||
<pre>T & [8]</pre>
|
||||
</td>
|
||||
<td valign="top" width="53%">
|
||||
<pre>T &</pre>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top" width="21%">
|
||||
<pre>const T &</pre>
|
||||
</td>
|
||||
<td valign="top" width="27%">
|
||||
<pre>const T &</pre>
|
||||
</td>
|
||||
<td valign="top" width="53%">
|
||||
<pre>const T &</pre>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>This allows us to build a primary template definition for "pair"
|
||||
that can contain non-reference types, reference types, and constant reference
|
||||
types:</p>
|
||||
<pre>template <typename T1, typename T2>
|
||||
struct pair
|
||||
{
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
|
||||
T1 first;
|
||||
T2 second;
|
||||
|
||||
pair(boost::add_reference<const T1>::type nfirst,
|
||||
boost::add_reference<const T2>::type nsecond)
|
||||
:first(nfirst), second(nsecond) { }
|
||||
};</pre>
|
||||
<p>Add back in the standard comparision operators, default constructor, and
|
||||
template copy constructor (which are all the same), and you have a std::pair
|
||||
that can hold reference types!</p>
|
||||
<p>This same extension <i>could</i> have been done using partial template
|
||||
specialization of "pair", but to specialize "pair" in this
|
||||
way would require three partial specializations, plus the primary template. Type
|
||||
traits allows us to define a single primary template that adjusts itself
|
||||
auto-magically to any of these partial specializations, instead of a brute-force
|
||||
partial specialization approach. Using type traits in this fashion allows
|
||||
programmers to delegate partial specialization to the type traits classes,
|
||||
resulting in code that is easier to maintain and easier to understand.</p>
|
||||
<h4>Conclusion</h4>
|
||||
<p>We hope that in this article we have been able to give you some idea of what
|
||||
type-traits are all about. A more complete listing of the available classes are
|
||||
in the boost documentation, along with further examples using type traits.
|
||||
Templates have enabled C++ uses to take the advantage of the code reuse that
|
||||
generic programming brings; hopefully this article has shown that generic
|
||||
programming does not have to sink to the lowest common denominator, and that
|
||||
templates can be optimal as well as generic.</p>
|
||||
<h4>Acknowledgements</h4>
|
||||
<p>The authors would like to thank Beman Dawes and Howard Hinnant for their
|
||||
helpful comments when preparing this article.</p>
|
||||
<h4>References</h4>
|
||||
<ol>
|
||||
<li>Nathan C. Myers, C++ Report, June 1995.</li>
|
||||
<li>The type traits library is based upon contributions by Steve Cleary, Beman
|
||||
Dawes, Howard Hinnant and John Maddock: it can be found at www.boost.org.</li>
|
||||
<li>A scalar type is an arithmetic type (i.e. a built-in integer or floating
|
||||
point type), an enumeration type, a pointer, a pointer to member, or a
|
||||
const- or volatile-qualified version of one of these types.</li>
|
||||
<li>This quote is from Donald Knuth, ACM Computing Surveys, December 1974, pg
|
||||
268.</li>
|
||||
<li>The test code is available as part of the boost utility library (see
|
||||
algo_opt_examples.cpp), the code was compiled with gcc 2.95 with all
|
||||
optimisations turned on, tests were conducted on a 400MHz Pentium II machine
|
||||
running Microsoft Windows 98.</li>
|
||||
<li>John Maddock and Howard Hinnant have submitted a "compressed_pair"
|
||||
library to Boost, which uses a technique similar to the one described here
|
||||
to hold references. Their pair also uses type traits to determine if any of
|
||||
the types are empty, and will derive instead of contain to conserve space --
|
||||
hence the name "compressed".</li>
|
||||
<li>This is actually an issue with the C++ Core Language Working Group (issue
|
||||
#106), submitted by Bjarne Stroustrup. The tentative resolution is to allow
|
||||
a "reference to a reference to T" to mean the same thing as a
|
||||
"reference to T", but only in template instantiation, in a method
|
||||
similar to multiple cv-qualifiers.</li>
|
||||
<li>For those of you who are wondering why this shouldn't be const-qualified,
|
||||
remember that references are always implicitly constant (for example, you
|
||||
can't re-assign a reference). Remember also that "const T &"
|
||||
is something completely different. For this reason, cv-qualifiers on
|
||||
template type arguments that are references are ignored.</li>
|
||||
</ol>
|
||||
<h2>Listing 1</h2>
|
||||
<pre>namespace detail{
|
||||
|
||||
template <bool b>
|
||||
struct copier
|
||||
{
|
||||
template<typename I1, typename I2>
|
||||
static I2 do_copy(I1 first,
|
||||
I1 last, I2 out);
|
||||
};
|
||||
|
||||
template <bool b>
|
||||
template<typename I1, typename I2>
|
||||
I2 copier<b>::do_copy(I1 first,
|
||||
I1 last,
|
||||
I2 out)
|
||||
{
|
||||
while(first != last)
|
||||
{
|
||||
*out = *first;
|
||||
++out;
|
||||
++first;
|
||||
}
|
||||
return out;
|
||||
}
|
||||
|
||||
template <>
|
||||
struct copier<true>
|
||||
{
|
||||
template<typename I1, typename I2>
|
||||
static I2* do_copy(I1* first, I1* last, I2* out)
|
||||
{
|
||||
memcpy(out, first, (last-first)*sizeof(I2));
|
||||
return out+(last-first);
|
||||
}
|
||||
};
|
||||
|
||||
}
|
||||
|
||||
template<typename I1, typename I2>
|
||||
inline I2 copy(I1 first, I1 last, I2 out)
|
||||
{
|
||||
typedef typename
|
||||
boost::remove_cv<
|
||||
typename std::iterator_traits<I1>
|
||||
::value_type>::type v1_t;
|
||||
|
||||
typedef typename
|
||||
boost::remove_cv<
|
||||
typename std::iterator_traits<I2>
|
||||
::value_type>::type v2_t;
|
||||
|
||||
enum{ can_opt =
|
||||
boost::is_same<v1_t, v2_t>::value
|
||||
&& boost::is_pointer<I1>::value
|
||||
&& boost::is_pointer<I2>::value
|
||||
&& boost::
|
||||
has_trivial_assign<v1_t>::value
|
||||
};
|
||||
|
||||
return detail::copier<can_opt>::
|
||||
do_copy(first, last, out);
|
||||
}</pre>
|
||||
<hr>
|
||||
<p><EFBFBD> Copyright John Maddock and Steve Cleary, 2000</p>
|
||||
|
||||
</body>
|
||||
|
||||
</html>
|
||||
@@ -1,155 +0,0 @@
|
||||
// (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000.
|
||||
// Use, modification and distribution are 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/libs/utility for most recent version including documentation.
|
||||
|
||||
// call_traits: defines typedefs for function usage
|
||||
// (see libs/utility/call_traits.htm)
|
||||
|
||||
/* Release notes:
|
||||
23rd July 2000:
|
||||
Fixed array specialization. (JM)
|
||||
Added Borland specific fixes for reference types
|
||||
(issue raised by Steve Cleary).
|
||||
*/
|
||||
|
||||
#ifndef BOOST_DETAIL_CALL_TRAITS_HPP
|
||||
#define BOOST_DETAIL_CALL_TRAITS_HPP
|
||||
|
||||
#ifndef BOOST_CONFIG_HPP
|
||||
#include <boost/config.hpp>
|
||||
#endif
|
||||
#include <cstddef>
|
||||
|
||||
#include <boost/type_traits/is_arithmetic.hpp>
|
||||
#include <boost/type_traits/is_pointer.hpp>
|
||||
#include <boost/detail/workaround.hpp>
|
||||
|
||||
namespace boost{
|
||||
|
||||
namespace detail{
|
||||
|
||||
template <typename T, bool small_>
|
||||
struct ct_imp2
|
||||
{
|
||||
typedef const T& param_type;
|
||||
};
|
||||
|
||||
template <typename T>
|
||||
struct ct_imp2<T, true>
|
||||
{
|
||||
typedef const T param_type;
|
||||
};
|
||||
|
||||
template <typename T, bool isp, bool b1>
|
||||
struct ct_imp
|
||||
{
|
||||
typedef const T& param_type;
|
||||
};
|
||||
|
||||
template <typename T, bool isp>
|
||||
struct ct_imp<T, isp, true>
|
||||
{
|
||||
typedef typename ct_imp2<T, sizeof(T) <= sizeof(void*)>::param_type param_type;
|
||||
};
|
||||
|
||||
template <typename T, bool b1>
|
||||
struct ct_imp<T, true, b1>
|
||||
{
|
||||
typedef T const param_type;
|
||||
};
|
||||
|
||||
}
|
||||
|
||||
template <typename T>
|
||||
struct call_traits
|
||||
{
|
||||
public:
|
||||
typedef T value_type;
|
||||
typedef T& reference;
|
||||
typedef const T& const_reference;
|
||||
//
|
||||
// C++ Builder workaround: we should be able to define a compile time
|
||||
// constant and pass that as a single template parameter to ct_imp<T,bool>,
|
||||
// however compiler bugs prevent this - instead pass three bool's to
|
||||
// ct_imp<T,bool,bool,bool> and add an extra partial specialisation
|
||||
// of ct_imp to handle the logic. (JM)
|
||||
typedef typename boost::detail::ct_imp<
|
||||
T,
|
||||
::boost::is_pointer<T>::value,
|
||||
::boost::is_arithmetic<T>::value
|
||||
>::param_type param_type;
|
||||
};
|
||||
|
||||
template <typename T>
|
||||
struct call_traits<T&>
|
||||
{
|
||||
typedef T& value_type;
|
||||
typedef T& reference;
|
||||
typedef const T& const_reference;
|
||||
typedef T& param_type; // hh removed const
|
||||
};
|
||||
|
||||
#if BOOST_WORKAROUND( __BORLANDC__, BOOST_TESTED_AT( 0x570 ) )
|
||||
// these are illegal specialisations; cv-qualifies applied to
|
||||
// references have no effect according to [8.3.2p1],
|
||||
// C++ Builder requires them though as it treats cv-qualified
|
||||
// references as distinct types...
|
||||
template <typename T>
|
||||
struct call_traits<T&const>
|
||||
{
|
||||
typedef T& value_type;
|
||||
typedef T& reference;
|
||||
typedef const T& const_reference;
|
||||
typedef T& param_type; // hh removed const
|
||||
};
|
||||
template <typename T>
|
||||
struct call_traits<T&volatile>
|
||||
{
|
||||
typedef T& value_type;
|
||||
typedef T& reference;
|
||||
typedef const T& const_reference;
|
||||
typedef T& param_type; // hh removed const
|
||||
};
|
||||
template <typename T>
|
||||
struct call_traits<T&const volatile>
|
||||
{
|
||||
typedef T& value_type;
|
||||
typedef T& reference;
|
||||
typedef const T& const_reference;
|
||||
typedef T& param_type; // hh removed const
|
||||
};
|
||||
#endif
|
||||
#if !defined(BOOST_NO_ARRAY_TYPE_SPECIALIZATIONS)
|
||||
template <typename T, std::size_t N>
|
||||
struct call_traits<T [N]>
|
||||
{
|
||||
private:
|
||||
typedef T array_type[N];
|
||||
public:
|
||||
// degrades array to pointer:
|
||||
typedef const T* value_type;
|
||||
typedef array_type& reference;
|
||||
typedef const array_type& const_reference;
|
||||
typedef const T* const param_type;
|
||||
};
|
||||
|
||||
template <typename T, std::size_t N>
|
||||
struct call_traits<const T [N]>
|
||||
{
|
||||
private:
|
||||
typedef const T array_type[N];
|
||||
public:
|
||||
// degrades array to pointer:
|
||||
typedef const T* value_type;
|
||||
typedef array_type& reference;
|
||||
typedef const array_type& const_reference;
|
||||
typedef const T* const param_type;
|
||||
};
|
||||
#endif
|
||||
|
||||
}
|
||||
|
||||
#endif // BOOST_DETAIL_CALL_TRAITS_HPP
|
||||
@@ -1,432 +0,0 @@
|
||||
// (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000.
|
||||
// Use, modification and distribution are 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/libs/utility for most recent version including documentation.
|
||||
|
||||
// compressed_pair: pair that "compresses" empty members
|
||||
// (see libs/utility/compressed_pair.htm)
|
||||
//
|
||||
// JM changes 25 Jan 2004:
|
||||
// For the case where T1 == T2 and both are empty, then first() and second()
|
||||
// should return different objects.
|
||||
// JM changes 25 Jan 2000:
|
||||
// Removed default arguments from compressed_pair_switch to get
|
||||
// C++ Builder 4 to accept them
|
||||
// rewriten swap to get gcc and C++ builder to compile.
|
||||
// added partial specialisations for case T1 == T2 to avoid duplicate constructor defs.
|
||||
|
||||
#ifndef BOOST_DETAIL_COMPRESSED_PAIR_HPP
|
||||
#define BOOST_DETAIL_COMPRESSED_PAIR_HPP
|
||||
|
||||
#include <algorithm>
|
||||
|
||||
#include <boost/type_traits/remove_cv.hpp>
|
||||
#include <boost/type_traits/is_empty.hpp>
|
||||
#include <boost/type_traits/is_same.hpp>
|
||||
#include <boost/call_traits.hpp>
|
||||
|
||||
namespace boost
|
||||
{
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair;
|
||||
|
||||
|
||||
// compressed_pair
|
||||
|
||||
namespace details
|
||||
{
|
||||
// JM altered 26 Jan 2000:
|
||||
template <class T1, class T2, bool IsSame, bool FirstEmpty, bool SecondEmpty>
|
||||
struct compressed_pair_switch;
|
||||
|
||||
template <class T1, class T2>
|
||||
struct compressed_pair_switch<T1, T2, false, false, false>
|
||||
{static const int value = 0;};
|
||||
|
||||
template <class T1, class T2>
|
||||
struct compressed_pair_switch<T1, T2, false, true, true>
|
||||
{static const int value = 3;};
|
||||
|
||||
template <class T1, class T2>
|
||||
struct compressed_pair_switch<T1, T2, false, true, false>
|
||||
{static const int value = 1;};
|
||||
|
||||
template <class T1, class T2>
|
||||
struct compressed_pair_switch<T1, T2, false, false, true>
|
||||
{static const int value = 2;};
|
||||
|
||||
template <class T1, class T2>
|
||||
struct compressed_pair_switch<T1, T2, true, true, true>
|
||||
{static const int value = 4;};
|
||||
|
||||
template <class T1, class T2>
|
||||
struct compressed_pair_switch<T1, T2, true, false, false>
|
||||
{static const int value = 5;};
|
||||
|
||||
template <class T1, class T2, int Version> class compressed_pair_imp;
|
||||
|
||||
#ifdef __GNUC__
|
||||
// workaround for GCC (JM):
|
||||
using std::swap;
|
||||
#endif
|
||||
//
|
||||
// can't call unqualified swap from within classname::swap
|
||||
// as Koenig lookup rules will find only the classname::swap
|
||||
// member function not the global declaration, so use cp_swap
|
||||
// as a forwarding function (JM):
|
||||
template <typename T>
|
||||
inline void cp_swap(T& t1, T& t2)
|
||||
{
|
||||
#ifndef __GNUC__
|
||||
using std::swap;
|
||||
#endif
|
||||
swap(t1, t2);
|
||||
}
|
||||
|
||||
// 0 derive from neither
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_imp<T1, T2, 0>
|
||||
{
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_imp() {}
|
||||
|
||||
compressed_pair_imp(first_param_type x, second_param_type y)
|
||||
: first_(x), second_(y) {}
|
||||
|
||||
compressed_pair_imp(first_param_type x)
|
||||
: first_(x) {}
|
||||
|
||||
compressed_pair_imp(second_param_type y)
|
||||
: second_(y) {}
|
||||
|
||||
first_reference first() {return first_;}
|
||||
first_const_reference first() const {return first_;}
|
||||
|
||||
second_reference second() {return second_;}
|
||||
second_const_reference second() const {return second_;}
|
||||
|
||||
void swap(::boost::compressed_pair<T1, T2>& y)
|
||||
{
|
||||
cp_swap(first_, y.first());
|
||||
cp_swap(second_, y.second());
|
||||
}
|
||||
private:
|
||||
first_type first_;
|
||||
second_type second_;
|
||||
};
|
||||
|
||||
// 1 derive from T1
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_imp<T1, T2, 1>
|
||||
: private ::boost::remove_cv<T1>::type
|
||||
{
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_imp() {}
|
||||
|
||||
compressed_pair_imp(first_param_type x, second_param_type y)
|
||||
: first_type(x), second_(y) {}
|
||||
|
||||
compressed_pair_imp(first_param_type x)
|
||||
: first_type(x) {}
|
||||
|
||||
compressed_pair_imp(second_param_type y)
|
||||
: second_(y) {}
|
||||
|
||||
first_reference first() {return *this;}
|
||||
first_const_reference first() const {return *this;}
|
||||
|
||||
second_reference second() {return second_;}
|
||||
second_const_reference second() const {return second_;}
|
||||
|
||||
void swap(::boost::compressed_pair<T1,T2>& y)
|
||||
{
|
||||
// no need to swap empty base class:
|
||||
cp_swap(second_, y.second());
|
||||
}
|
||||
private:
|
||||
second_type second_;
|
||||
};
|
||||
|
||||
// 2 derive from T2
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_imp<T1, T2, 2>
|
||||
: private ::boost::remove_cv<T2>::type
|
||||
{
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_imp() {}
|
||||
|
||||
compressed_pair_imp(first_param_type x, second_param_type y)
|
||||
: second_type(y), first_(x) {}
|
||||
|
||||
compressed_pair_imp(first_param_type x)
|
||||
: first_(x) {}
|
||||
|
||||
compressed_pair_imp(second_param_type y)
|
||||
: second_type(y) {}
|
||||
|
||||
first_reference first() {return first_;}
|
||||
first_const_reference first() const {return first_;}
|
||||
|
||||
second_reference second() {return *this;}
|
||||
second_const_reference second() const {return *this;}
|
||||
|
||||
void swap(::boost::compressed_pair<T1,T2>& y)
|
||||
{
|
||||
// no need to swap empty base class:
|
||||
cp_swap(first_, y.first());
|
||||
}
|
||||
|
||||
private:
|
||||
first_type first_;
|
||||
};
|
||||
|
||||
// 3 derive from T1 and T2
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_imp<T1, T2, 3>
|
||||
: private ::boost::remove_cv<T1>::type,
|
||||
private ::boost::remove_cv<T2>::type
|
||||
{
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_imp() {}
|
||||
|
||||
compressed_pair_imp(first_param_type x, second_param_type y)
|
||||
: first_type(x), second_type(y) {}
|
||||
|
||||
compressed_pair_imp(first_param_type x)
|
||||
: first_type(x) {}
|
||||
|
||||
compressed_pair_imp(second_param_type y)
|
||||
: second_type(y) {}
|
||||
|
||||
first_reference first() {return *this;}
|
||||
first_const_reference first() const {return *this;}
|
||||
|
||||
second_reference second() {return *this;}
|
||||
second_const_reference second() const {return *this;}
|
||||
//
|
||||
// no need to swap empty bases:
|
||||
void swap(::boost::compressed_pair<T1,T2>&) {}
|
||||
};
|
||||
|
||||
// JM
|
||||
// 4 T1 == T2, T1 and T2 both empty
|
||||
// Note does not actually store an instance of T2 at all -
|
||||
// but reuses T1 base class for both first() and second().
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_imp<T1, T2, 4>
|
||||
: private ::boost::remove_cv<T1>::type
|
||||
{
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_imp() {}
|
||||
|
||||
compressed_pair_imp(first_param_type x, second_param_type y)
|
||||
: first_type(x), m_second(y) {}
|
||||
|
||||
compressed_pair_imp(first_param_type x)
|
||||
: first_type(x), m_second(x) {}
|
||||
|
||||
first_reference first() {return *this;}
|
||||
first_const_reference first() const {return *this;}
|
||||
|
||||
second_reference second() {return m_second;}
|
||||
second_const_reference second() const {return m_second;}
|
||||
|
||||
void swap(::boost::compressed_pair<T1,T2>&) {}
|
||||
private:
|
||||
T2 m_second;
|
||||
};
|
||||
|
||||
// 5 T1 == T2 and are not empty: //JM
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_imp<T1, T2, 5>
|
||||
{
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_imp() {}
|
||||
|
||||
compressed_pair_imp(first_param_type x, second_param_type y)
|
||||
: first_(x), second_(y) {}
|
||||
|
||||
compressed_pair_imp(first_param_type x)
|
||||
: first_(x), second_(x) {}
|
||||
|
||||
first_reference first() {return first_;}
|
||||
first_const_reference first() const {return first_;}
|
||||
|
||||
second_reference second() {return second_;}
|
||||
second_const_reference second() const {return second_;}
|
||||
|
||||
void swap(::boost::compressed_pair<T1, T2>& y)
|
||||
{
|
||||
cp_swap(first_, y.first());
|
||||
cp_swap(second_, y.second());
|
||||
}
|
||||
private:
|
||||
first_type first_;
|
||||
second_type second_;
|
||||
};
|
||||
|
||||
} // details
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair
|
||||
: private ::boost::details::compressed_pair_imp<T1, T2,
|
||||
::boost::details::compressed_pair_switch<
|
||||
T1,
|
||||
T2,
|
||||
::boost::is_same<typename remove_cv<T1>::type, typename remove_cv<T2>::type>::value,
|
||||
::boost::is_empty<T1>::value,
|
||||
::boost::is_empty<T2>::value>::value>
|
||||
{
|
||||
private:
|
||||
typedef details::compressed_pair_imp<T1, T2,
|
||||
::boost::details::compressed_pair_switch<
|
||||
T1,
|
||||
T2,
|
||||
::boost::is_same<typename remove_cv<T1>::type, typename remove_cv<T2>::type>::value,
|
||||
::boost::is_empty<T1>::value,
|
||||
::boost::is_empty<T2>::value>::value> base;
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair() : base() {}
|
||||
compressed_pair(first_param_type x, second_param_type y) : base(x, y) {}
|
||||
explicit compressed_pair(first_param_type x) : base(x) {}
|
||||
explicit compressed_pair(second_param_type y) : base(y) {}
|
||||
|
||||
first_reference first() {return base::first();}
|
||||
first_const_reference first() const {return base::first();}
|
||||
|
||||
second_reference second() {return base::second();}
|
||||
second_const_reference second() const {return base::second();}
|
||||
|
||||
void swap(compressed_pair& y) { base::swap(y); }
|
||||
};
|
||||
|
||||
// JM
|
||||
// Partial specialisation for case where T1 == T2:
|
||||
//
|
||||
template <class T>
|
||||
class compressed_pair<T, T>
|
||||
: private details::compressed_pair_imp<T, T,
|
||||
::boost::details::compressed_pair_switch<
|
||||
T,
|
||||
T,
|
||||
::boost::is_same<typename remove_cv<T>::type, typename remove_cv<T>::type>::value,
|
||||
::boost::is_empty<T>::value,
|
||||
::boost::is_empty<T>::value>::value>
|
||||
{
|
||||
private:
|
||||
typedef details::compressed_pair_imp<T, T,
|
||||
::boost::details::compressed_pair_switch<
|
||||
T,
|
||||
T,
|
||||
::boost::is_same<typename remove_cv<T>::type, typename remove_cv<T>::type>::value,
|
||||
::boost::is_empty<T>::value,
|
||||
::boost::is_empty<T>::value>::value> base;
|
||||
public:
|
||||
typedef T first_type;
|
||||
typedef T second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair() : base() {}
|
||||
compressed_pair(first_param_type x, second_param_type y) : base(x, y) {}
|
||||
#if !(defined(__SUNPRO_CC) && (__SUNPRO_CC <= 0x530))
|
||||
explicit
|
||||
#endif
|
||||
compressed_pair(first_param_type x) : base(x) {}
|
||||
|
||||
first_reference first() {return base::first();}
|
||||
first_const_reference first() const {return base::first();}
|
||||
|
||||
second_reference second() {return base::second();}
|
||||
second_const_reference second() const {return base::second();}
|
||||
|
||||
void swap(::boost::compressed_pair<T,T>& y) { base::swap(y); }
|
||||
};
|
||||
|
||||
template <class T1, class T2>
|
||||
inline
|
||||
void
|
||||
swap(compressed_pair<T1, T2>& x, compressed_pair<T1, T2>& y)
|
||||
{
|
||||
x.swap(y);
|
||||
}
|
||||
|
||||
} // boost
|
||||
|
||||
#endif // BOOST_DETAIL_COMPRESSED_PAIR_HPP
|
||||
|
||||
@@ -1,168 +0,0 @@
|
||||
// (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000.
|
||||
// Use, modification and distribution are 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/libs/utility for most recent version including documentation.
|
||||
//
|
||||
// Crippled version for crippled compilers:
|
||||
// see libs/utility/call_traits.htm
|
||||
//
|
||||
|
||||
/* Release notes:
|
||||
01st October 2000:
|
||||
Fixed call_traits on VC6, using "poor man's partial specialisation",
|
||||
using ideas taken from "Generative programming" by Krzysztof Czarnecki
|
||||
& Ulrich Eisenecker.
|
||||
*/
|
||||
|
||||
#ifndef BOOST_OB_CALL_TRAITS_HPP
|
||||
#define BOOST_OB_CALL_TRAITS_HPP
|
||||
|
||||
#ifndef BOOST_CONFIG_HPP
|
||||
#include <boost/config.hpp>
|
||||
#endif
|
||||
|
||||
#ifndef BOOST_ARITHMETIC_TYPE_TRAITS_HPP
|
||||
#include <boost/type_traits/arithmetic_traits.hpp>
|
||||
#endif
|
||||
#ifndef BOOST_COMPOSITE_TYPE_TRAITS_HPP
|
||||
#include <boost/type_traits/composite_traits.hpp>
|
||||
#endif
|
||||
|
||||
namespace boost{
|
||||
|
||||
#ifdef BOOST_MSVC6_MEMBER_TEMPLATES
|
||||
//
|
||||
// use member templates to emulate
|
||||
// partial specialisation:
|
||||
//
|
||||
namespace detail{
|
||||
|
||||
template <class T>
|
||||
struct standard_call_traits
|
||||
{
|
||||
typedef T value_type;
|
||||
typedef T& reference;
|
||||
typedef const T& const_reference;
|
||||
typedef const T& param_type;
|
||||
};
|
||||
template <class T>
|
||||
struct simple_call_traits
|
||||
{
|
||||
typedef T value_type;
|
||||
typedef T& reference;
|
||||
typedef const T& const_reference;
|
||||
typedef const T param_type;
|
||||
};
|
||||
template <class T>
|
||||
struct reference_call_traits
|
||||
{
|
||||
typedef T value_type;
|
||||
typedef T reference;
|
||||
typedef T const_reference;
|
||||
typedef T param_type;
|
||||
};
|
||||
|
||||
template <bool pointer, bool arithmetic, bool reference>
|
||||
struct call_traits_chooser
|
||||
{
|
||||
template <class T>
|
||||
struct rebind
|
||||
{
|
||||
typedef standard_call_traits<T> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <>
|
||||
struct call_traits_chooser<true, false, false>
|
||||
{
|
||||
template <class T>
|
||||
struct rebind
|
||||
{
|
||||
typedef simple_call_traits<T> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <>
|
||||
struct call_traits_chooser<false, false, true>
|
||||
{
|
||||
template <class T>
|
||||
struct rebind
|
||||
{
|
||||
typedef reference_call_traits<T> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <bool size_is_small>
|
||||
struct call_traits_sizeof_chooser2
|
||||
{
|
||||
template <class T>
|
||||
struct small_rebind
|
||||
{
|
||||
typedef simple_call_traits<T> small_type;
|
||||
};
|
||||
};
|
||||
|
||||
template<>
|
||||
struct call_traits_sizeof_chooser2<false>
|
||||
{
|
||||
template <class T>
|
||||
struct small_rebind
|
||||
{
|
||||
typedef standard_call_traits<T> small_type;
|
||||
};
|
||||
};
|
||||
|
||||
template <>
|
||||
struct call_traits_chooser<false, true, false>
|
||||
{
|
||||
template <class T>
|
||||
struct rebind
|
||||
{
|
||||
enum { sizeof_choice = (sizeof(T) <= sizeof(void*)) };
|
||||
typedef call_traits_sizeof_chooser2<(sizeof(T) <= sizeof(void*))> chooser;
|
||||
typedef typename chooser::template small_rebind<T> bound_type;
|
||||
typedef typename bound_type::small_type type;
|
||||
};
|
||||
};
|
||||
|
||||
} // namespace detail
|
||||
template <typename T>
|
||||
struct call_traits
|
||||
{
|
||||
private:
|
||||
typedef detail::call_traits_chooser<
|
||||
::boost::is_pointer<T>::value,
|
||||
::boost::is_arithmetic<T>::value,
|
||||
::boost::is_reference<T>::value
|
||||
> chooser;
|
||||
typedef typename chooser::template rebind<T> bound_type;
|
||||
typedef typename bound_type::type call_traits_type;
|
||||
public:
|
||||
typedef typename call_traits_type::value_type value_type;
|
||||
typedef typename call_traits_type::reference reference;
|
||||
typedef typename call_traits_type::const_reference const_reference;
|
||||
typedef typename call_traits_type::param_type param_type;
|
||||
};
|
||||
|
||||
#else
|
||||
//
|
||||
// sorry call_traits is completely non-functional
|
||||
// blame your broken compiler:
|
||||
//
|
||||
|
||||
template <typename T>
|
||||
struct call_traits
|
||||
{
|
||||
typedef T value_type;
|
||||
typedef T& reference;
|
||||
typedef const T& const_reference;
|
||||
typedef const T& param_type;
|
||||
};
|
||||
|
||||
#endif // member templates
|
||||
|
||||
}
|
||||
|
||||
#endif // BOOST_OB_CALL_TRAITS_HPP
|
||||
@@ -1,510 +0,0 @@
|
||||
// (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000.
|
||||
// Use, modification and distribution are 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/libs/utility for most recent version including documentation.
|
||||
// see libs/utility/compressed_pair.hpp
|
||||
//
|
||||
/* Release notes:
|
||||
20 Jan 2001:
|
||||
Fixed obvious bugs (David Abrahams)
|
||||
07 Oct 2000:
|
||||
Added better single argument constructor support.
|
||||
03 Oct 2000:
|
||||
Added VC6 support (JM).
|
||||
23rd July 2000:
|
||||
Additional comments added. (JM)
|
||||
Jan 2000:
|
||||
Original version: this version crippled for use with crippled compilers
|
||||
- John Maddock Jan 2000.
|
||||
*/
|
||||
|
||||
|
||||
#ifndef BOOST_OB_COMPRESSED_PAIR_HPP
|
||||
#define BOOST_OB_COMPRESSED_PAIR_HPP
|
||||
|
||||
#include <algorithm>
|
||||
#ifndef BOOST_OBJECT_TYPE_TRAITS_HPP
|
||||
#include <boost/type_traits/object_traits.hpp>
|
||||
#endif
|
||||
#ifndef BOOST_SAME_TRAITS_HPP
|
||||
#include <boost/type_traits/same_traits.hpp>
|
||||
#endif
|
||||
#ifndef BOOST_CALL_TRAITS_HPP
|
||||
#include <boost/call_traits.hpp>
|
||||
#endif
|
||||
|
||||
namespace boost
|
||||
{
|
||||
#ifdef BOOST_MSVC6_MEMBER_TEMPLATES
|
||||
//
|
||||
// use member templates to emulate
|
||||
// partial specialisation. Note that due to
|
||||
// problems with overload resolution with VC6
|
||||
// each of the compressed_pair versions that follow
|
||||
// have one template single-argument constructor
|
||||
// in place of two specific constructors:
|
||||
//
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair;
|
||||
|
||||
namespace detail{
|
||||
|
||||
template <class A, class T1, class T2>
|
||||
struct best_conversion_traits
|
||||
{
|
||||
typedef char one;
|
||||
typedef char (&two)[2];
|
||||
static A a;
|
||||
static one test(T1);
|
||||
static two test(T2);
|
||||
|
||||
enum { value = sizeof(test(a)) };
|
||||
};
|
||||
|
||||
template <int>
|
||||
struct init_one;
|
||||
|
||||
template <>
|
||||
struct init_one<1>
|
||||
{
|
||||
template <class A, class T1, class T2>
|
||||
static void init(const A& a, T1* p1, T2*)
|
||||
{
|
||||
*p1 = a;
|
||||
}
|
||||
};
|
||||
|
||||
template <>
|
||||
struct init_one<2>
|
||||
{
|
||||
template <class A, class T1, class T2>
|
||||
static void init(const A& a, T1*, T2* p2)
|
||||
{
|
||||
*p2 = a;
|
||||
}
|
||||
};
|
||||
|
||||
|
||||
// T1 != T2, both non-empty
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_0
|
||||
{
|
||||
private:
|
||||
T1 _first;
|
||||
T2 _second;
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_0() : _first(), _second() {}
|
||||
compressed_pair_0(first_param_type x, second_param_type y) : _first(x), _second(y) {}
|
||||
template <class A>
|
||||
explicit compressed_pair_0(const A& val)
|
||||
{
|
||||
init_one<best_conversion_traits<A, T1, T2>::value>::init(val, &_first, &_second);
|
||||
}
|
||||
compressed_pair_0(const ::boost::compressed_pair<T1,T2>& x)
|
||||
: _first(x.first()), _second(x.second()) {}
|
||||
|
||||
#if 0
|
||||
compressed_pair_0& operator=(const compressed_pair_0& x) {
|
||||
cout << "assigning compressed pair 0" << endl;
|
||||
_first = x._first;
|
||||
_second = x._second;
|
||||
cout << "finished assigning compressed pair 0" << endl;
|
||||
return *this;
|
||||
}
|
||||
#endif
|
||||
|
||||
first_reference first() { return _first; }
|
||||
first_const_reference first() const { return _first; }
|
||||
|
||||
second_reference second() { return _second; }
|
||||
second_const_reference second() const { return _second; }
|
||||
|
||||
void swap(compressed_pair_0& y)
|
||||
{
|
||||
using std::swap;
|
||||
swap(_first, y._first);
|
||||
swap(_second, y._second);
|
||||
}
|
||||
};
|
||||
|
||||
// T1 != T2, T2 empty
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_1 : T2
|
||||
{
|
||||
private:
|
||||
T1 _first;
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_1() : T2(), _first() {}
|
||||
compressed_pair_1(first_param_type x, second_param_type y) : T2(y), _first(x) {}
|
||||
|
||||
template <class A>
|
||||
explicit compressed_pair_1(const A& val)
|
||||
{
|
||||
init_one<best_conversion_traits<A, T1, T2>::value>::init(val, &_first, static_cast<T2*>(this));
|
||||
}
|
||||
|
||||
compressed_pair_1(const ::boost::compressed_pair<T1,T2>& x)
|
||||
: T2(x.second()), _first(x.first()) {}
|
||||
|
||||
#if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
|
||||
// Total weirdness. If the assignment to _first is moved after
|
||||
// the call to the inherited operator=, then this breaks graph/test/graph.cpp
|
||||
// by way of iterator_adaptor.
|
||||
compressed_pair_1& operator=(const compressed_pair_1& x) {
|
||||
_first = x._first;
|
||||
T2::operator=(x);
|
||||
return *this;
|
||||
}
|
||||
#endif
|
||||
|
||||
first_reference first() { return _first; }
|
||||
first_const_reference first() const { return _first; }
|
||||
|
||||
second_reference second() { return *this; }
|
||||
second_const_reference second() const { return *this; }
|
||||
|
||||
void swap(compressed_pair_1& y)
|
||||
{
|
||||
// no need to swap empty base class:
|
||||
using std::swap;
|
||||
swap(_first, y._first);
|
||||
}
|
||||
};
|
||||
|
||||
// T1 != T2, T1 empty
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_2 : T1
|
||||
{
|
||||
private:
|
||||
T2 _second;
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_2() : T1(), _second() {}
|
||||
compressed_pair_2(first_param_type x, second_param_type y) : T1(x), _second(y) {}
|
||||
template <class A>
|
||||
explicit compressed_pair_2(const A& val)
|
||||
{
|
||||
init_one<best_conversion_traits<A, T1, T2>::value>::init(val, static_cast<T1*>(this), &_second);
|
||||
}
|
||||
compressed_pair_2(const ::boost::compressed_pair<T1,T2>& x)
|
||||
: T1(x.first()), _second(x.second()) {}
|
||||
|
||||
#if 0
|
||||
compressed_pair_2& operator=(const compressed_pair_2& x) {
|
||||
cout << "assigning compressed pair 2" << endl;
|
||||
T1::operator=(x);
|
||||
_second = x._second;
|
||||
cout << "finished assigning compressed pair 2" << endl;
|
||||
return *this;
|
||||
}
|
||||
#endif
|
||||
first_reference first() { return *this; }
|
||||
first_const_reference first() const { return *this; }
|
||||
|
||||
second_reference second() { return _second; }
|
||||
second_const_reference second() const { return _second; }
|
||||
|
||||
void swap(compressed_pair_2& y)
|
||||
{
|
||||
// no need to swap empty base class:
|
||||
using std::swap;
|
||||
swap(_second, y._second);
|
||||
}
|
||||
};
|
||||
|
||||
// T1 != T2, both empty
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_3 : T1, T2
|
||||
{
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_3() : T1(), T2() {}
|
||||
compressed_pair_3(first_param_type x, second_param_type y) : T1(x), T2(y) {}
|
||||
template <class A>
|
||||
explicit compressed_pair_3(const A& val)
|
||||
{
|
||||
init_one<best_conversion_traits<A, T1, T2>::value>::init(val, static_cast<T1*>(this), static_cast<T2*>(this));
|
||||
}
|
||||
compressed_pair_3(const ::boost::compressed_pair<T1,T2>& x)
|
||||
: T1(x.first()), T2(x.second()) {}
|
||||
|
||||
first_reference first() { return *this; }
|
||||
first_const_reference first() const { return *this; }
|
||||
|
||||
second_reference second() { return *this; }
|
||||
second_const_reference second() const { return *this; }
|
||||
|
||||
void swap(compressed_pair_3& y)
|
||||
{
|
||||
// no need to swap empty base classes:
|
||||
}
|
||||
};
|
||||
|
||||
// T1 == T2, and empty
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_4 : T1
|
||||
{
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_4() : T1() {}
|
||||
compressed_pair_4(first_param_type x, second_param_type y) : T1(x), m_second(y) {}
|
||||
// only one single argument constructor since T1 == T2
|
||||
explicit compressed_pair_4(first_param_type x) : T1(x), m_second(x) {}
|
||||
compressed_pair_4(const ::boost::compressed_pair<T1,T2>& x)
|
||||
: T1(x.first()), m_second(x.second()) {}
|
||||
|
||||
first_reference first() { return *this; }
|
||||
first_const_reference first() const { return *this; }
|
||||
|
||||
second_reference second() { return m_second; }
|
||||
second_const_reference second() const { return m_second; }
|
||||
|
||||
void swap(compressed_pair_4& y)
|
||||
{
|
||||
// no need to swap empty base classes:
|
||||
}
|
||||
private:
|
||||
T2 m_second;
|
||||
};
|
||||
|
||||
// T1 == T2, not empty
|
||||
template <class T1, class T2>
|
||||
class compressed_pair_5
|
||||
{
|
||||
private:
|
||||
T1 _first;
|
||||
T2 _second;
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair_5() : _first(), _second() {}
|
||||
compressed_pair_5(first_param_type x, second_param_type y) : _first(x), _second(y) {}
|
||||
// only one single argument constructor since T1 == T2
|
||||
explicit compressed_pair_5(first_param_type x) : _first(x), _second(x) {}
|
||||
compressed_pair_5(const ::boost::compressed_pair<T1,T2>& c)
|
||||
: _first(c.first()), _second(c.second()) {}
|
||||
|
||||
first_reference first() { return _first; }
|
||||
first_const_reference first() const { return _first; }
|
||||
|
||||
second_reference second() { return _second; }
|
||||
second_const_reference second() const { return _second; }
|
||||
|
||||
void swap(compressed_pair_5& y)
|
||||
{
|
||||
using std::swap;
|
||||
swap(_first, y._first);
|
||||
swap(_second, y._second);
|
||||
}
|
||||
};
|
||||
|
||||
template <bool e1, bool e2, bool same>
|
||||
struct compressed_pair_chooser
|
||||
{
|
||||
template <class T1, class T2>
|
||||
struct rebind
|
||||
{
|
||||
typedef compressed_pair_0<T1, T2> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <>
|
||||
struct compressed_pair_chooser<false, true, false>
|
||||
{
|
||||
template <class T1, class T2>
|
||||
struct rebind
|
||||
{
|
||||
typedef compressed_pair_1<T1, T2> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <>
|
||||
struct compressed_pair_chooser<true, false, false>
|
||||
{
|
||||
template <class T1, class T2>
|
||||
struct rebind
|
||||
{
|
||||
typedef compressed_pair_2<T1, T2> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <>
|
||||
struct compressed_pair_chooser<true, true, false>
|
||||
{
|
||||
template <class T1, class T2>
|
||||
struct rebind
|
||||
{
|
||||
typedef compressed_pair_3<T1, T2> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <>
|
||||
struct compressed_pair_chooser<true, true, true>
|
||||
{
|
||||
template <class T1, class T2>
|
||||
struct rebind
|
||||
{
|
||||
typedef compressed_pair_4<T1, T2> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <>
|
||||
struct compressed_pair_chooser<false, false, true>
|
||||
{
|
||||
template <class T1, class T2>
|
||||
struct rebind
|
||||
{
|
||||
typedef compressed_pair_5<T1, T2> type;
|
||||
};
|
||||
};
|
||||
|
||||
template <class T1, class T2>
|
||||
struct compressed_pair_traits
|
||||
{
|
||||
private:
|
||||
typedef compressed_pair_chooser<is_empty<T1>::value, is_empty<T2>::value, is_same<T1,T2>::value> chooser;
|
||||
typedef typename chooser::template rebind<T1, T2> bound_type;
|
||||
public:
|
||||
typedef typename bound_type::type type;
|
||||
};
|
||||
|
||||
} // namespace detail
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair : public detail::compressed_pair_traits<T1, T2>::type
|
||||
{
|
||||
private:
|
||||
typedef typename detail::compressed_pair_traits<T1, T2>::type base_type;
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair() : base_type() {}
|
||||
compressed_pair(first_param_type x, second_param_type y) : base_type(x, y) {}
|
||||
template <class A>
|
||||
explicit compressed_pair(const A& x) : base_type(x){}
|
||||
|
||||
first_reference first() { return base_type::first(); }
|
||||
first_const_reference first() const { return base_type::first(); }
|
||||
|
||||
second_reference second() { return base_type::second(); }
|
||||
second_const_reference second() const { return base_type::second(); }
|
||||
};
|
||||
|
||||
template <class T1, class T2>
|
||||
inline void swap(compressed_pair<T1, T2>& x, compressed_pair<T1, T2>& y)
|
||||
{
|
||||
x.swap(y);
|
||||
}
|
||||
|
||||
#else
|
||||
// no partial specialisation, no member templates:
|
||||
|
||||
template <class T1, class T2>
|
||||
class compressed_pair
|
||||
{
|
||||
private:
|
||||
T1 _first;
|
||||
T2 _second;
|
||||
public:
|
||||
typedef T1 first_type;
|
||||
typedef T2 second_type;
|
||||
typedef typename call_traits<first_type>::param_type first_param_type;
|
||||
typedef typename call_traits<second_type>::param_type second_param_type;
|
||||
typedef typename call_traits<first_type>::reference first_reference;
|
||||
typedef typename call_traits<second_type>::reference second_reference;
|
||||
typedef typename call_traits<first_type>::const_reference first_const_reference;
|
||||
typedef typename call_traits<second_type>::const_reference second_const_reference;
|
||||
|
||||
compressed_pair() : _first(), _second() {}
|
||||
compressed_pair(first_param_type x, second_param_type y) : _first(x), _second(y) {}
|
||||
explicit compressed_pair(first_param_type x) : _first(x), _second() {}
|
||||
// can't define this in case T1 == T2:
|
||||
// explicit compressed_pair(second_param_type y) : _first(), _second(y) {}
|
||||
|
||||
first_reference first() { return _first; }
|
||||
first_const_reference first() const { return _first; }
|
||||
|
||||
second_reference second() { return _second; }
|
||||
second_const_reference second() const { return _second; }
|
||||
|
||||
void swap(compressed_pair& y)
|
||||
{
|
||||
using std::swap;
|
||||
swap(_first, y._first);
|
||||
swap(_second, y._second);
|
||||
}
|
||||
};
|
||||
|
||||
template <class T1, class T2>
|
||||
inline void swap(compressed_pair<T1, T2>& x, compressed_pair<T1, T2>& y)
|
||||
{
|
||||
x.swap(y);
|
||||
}
|
||||
|
||||
#endif
|
||||
|
||||
} // boost
|
||||
|
||||
#endif // BOOST_OB_COMPRESSED_PAIR_HPP
|
||||
|
||||
|
||||
|
||||
Reference in New Issue
Block a user