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| <h2><span class="refentrytitle">Macro BOOST_TTI_TRAIT_HAS_TEMPLATE</span></h2> |
| <p>BOOST_TTI_TRAIT_HAS_TEMPLATE — Expands to a metafunction which tests whether an inner class template with a particular name exists. </p> |
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| <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> |
| <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="header/boost/tti/has_template_hpp.html" title="Header <boost/tti/has_template.hpp>">boost/tti/has_template.hpp</a>> |
| |
| </span>BOOST_TTI_TRAIT_HAS_TEMPLATE(trait, ...)</pre></div> |
| <div class="refsect1"> |
| <a name="idp103068688"></a><h2>Description</h2> |
| <p>trait = the name of the metafunction. ... = variadic parameters. The first variadic parameter is the inner class template name. |
| |
| Following variadic parameters are optional. |
| |
| If no following variadic parameters exist, then the inner class template |
| being introspected must be all template type parameters ( template parameters |
| starting with `class` or `typename` ) and any number of template type parameters |
| can occur. |
| |
| If the second variadic parameter is BOOST_PP_NIL and no other variadic |
| parameter is given, then just as in the previous case the inner class template |
| being introspected must be all template type parameters ( template parameters |
| starting with `class` or `typename` ) and any number of template type parameters |
| can occur. This form is allowed in order to be consistent with using the |
| non-variadic form of this macro. |
| |
| If the second variadic parameter is a Boost preprocessor library array and no other |
| variadic parameter is given, then the inner class template must have its template |
| parameters matching the sequence in the tuple portion of the Boost PP array. This |
| form is allowed in order to be consistent with using the non-variadic form of this |
| macro. |
| |
| Otherwise the inner class template must have its template parameters matching the |
| sequence of the optional variadic parameters. |
| </p> |
| <p>generates a metafunction called "trait" where 'trait' is the first macro parameter. template<class BOOST_TTI_TP_T> |
| struct trait |
| { |
| static const value = unspecified; |
| typedef mpl::bool_<true-or-false> type; |
| }; |
| |
| The metafunction types and return: |
| |
| BOOST_TTI_TP_T = the enclosing type in which to look for our 'name'. |
| |
| returns = 'value' is true if the 'name' template exists within the enclosing type, |
| otherwise 'value' is false. |
| </p> |
| <p>Examples:</p> |
| <p>1) Search for an inner class template called 'MyTemplate', with all template type parameters, nested within the class 'MyClass' using a metafunction name of 'MyMeta'.</p> |
| <p>BOOST_TTI_TRAIT_HAS_TEMPLATE(MyMeta,MyTemplate)</p> |
| <p>or</p> |
| <p>BOOST_TTI_TRAIT_HAS_TEMPLATE(MyMeta,MyTemplate,BOOST_PP_NIL) // Non-variadic macro form</p> |
| <p>MyMeta<MyClass>::value</p> |
| <p>is a compile time boolean constant which is either 'true' or 'false' if the nested template exists.</p> |
| <p>2) Search for an inner class template called 'MyTemplate', with template parameters of 'class T,int x,template<class> class U', nested within the class 'MyClass' using a metafunction name of 'MyMeta'.</p> |
| <p>BOOST_TTI_TRAIT_HAS_TEMPLATE(MyMeta,MyTemplate,class,int,template<class> class)</p> |
| <p>or</p> |
| <p>BOOST_TTI_TRAIT_HAS_TEMPLATE(MyMeta,MyTemplate,(3,(class,int,template<class> class))) // Non-variadic macro form</p> |
| <p>MyMeta<MyClass>::value</p> |
| <p>is a compile time boolean constant which is either 'true' or 'false' if the nested template exists. </p> |
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| <td align="right"><div class="copyright-footer">Copyright © 2011-2013 Tropic Software |
| East Inc<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>) |
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