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135 lines
2.9 KiB
135 lines
2.9 KiB
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#ifndef BOOST_MPL_IF_HPP_INCLUDED |
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#define BOOST_MPL_IF_HPP_INCLUDED |
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// Copyright Aleksey Gurtovoy 2000-2004 |
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// |
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// Distributed under the Boost Software License, Version 1.0. |
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// (See accompanying file LICENSE_1_0.txt or copy at |
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// http://www.boost.org/LICENSE_1_0.txt) |
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// |
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// See http://www.boost.org/libs/mpl for documentation. |
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// $Id: if.hpp 49267 2008-10-11 06:19:02Z agurtovoy $ |
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// $Date: 2008-10-11 02:19:02 -0400 (Sat, 11 Oct 2008) $ |
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// $Revision: 49267 $ |
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#include <boost/mpl/aux_/value_wknd.hpp> |
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#include <boost/mpl/aux_/static_cast.hpp> |
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#include <boost/mpl/aux_/na_spec.hpp> |
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#include <boost/mpl/aux_/lambda_support.hpp> |
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#include <boost/mpl/aux_/config/integral.hpp> |
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#include <boost/mpl/aux_/config/ctps.hpp> |
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#include <boost/mpl/aux_/config/workaround.hpp> |
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namespace boost { namespace mpl { |
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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
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template< |
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bool C |
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, typename T1 |
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, typename T2 |
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> |
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struct if_c |
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{ |
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typedef T1 type; |
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}; |
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template< |
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typename T1 |
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, typename T2 |
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> |
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struct if_c<false,T1,T2> |
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{ |
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typedef T2 type; |
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}; |
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// agurt, 05/sep/04: nondescriptive parameter names for the sake of DigitalMars |
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// (and possibly MWCW < 8.0); see http://article.gmane.org/gmane.comp.lib.boost.devel/108959 |
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template< |
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typename BOOST_MPL_AUX_NA_PARAM(T1) |
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, typename BOOST_MPL_AUX_NA_PARAM(T2) |
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, typename BOOST_MPL_AUX_NA_PARAM(T3) |
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> |
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struct if_ |
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{ |
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private: |
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// agurt, 02/jan/03: two-step 'type' definition for the sake of aCC |
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typedef if_c< |
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#if defined(BOOST_MPL_CFG_BCC_INTEGRAL_CONSTANTS) |
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BOOST_MPL_AUX_VALUE_WKND(T1)::value |
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#else |
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BOOST_MPL_AUX_STATIC_CAST(bool, BOOST_MPL_AUX_VALUE_WKND(T1)::value) |
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#endif |
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, T2 |
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, T3 |
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> almost_type_; |
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public: |
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typedef typename almost_type_::type type; |
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BOOST_MPL_AUX_LAMBDA_SUPPORT(3,if_,(T1,T2,T3)) |
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}; |
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#else |
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// no partial class template specialization |
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namespace aux { |
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template< bool C > |
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struct if_impl |
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{ |
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template< typename T1, typename T2 > struct result_ |
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{ |
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typedef T1 type; |
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}; |
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}; |
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template<> |
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struct if_impl<false> |
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{ |
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template< typename T1, typename T2 > struct result_ |
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{ |
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typedef T2 type; |
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}; |
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}; |
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} // namespace aux |
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template< |
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bool C_ |
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, typename T1 |
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, typename T2 |
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> |
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struct if_c |
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{ |
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typedef typename aux::if_impl< C_ > |
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::template result_<T1,T2>::type type; |
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}; |
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// (almost) copy & paste in order to save one more |
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// recursively nested template instantiation to user |
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template< |
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typename BOOST_MPL_AUX_NA_PARAM(C_) |
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, typename BOOST_MPL_AUX_NA_PARAM(T1) |
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, typename BOOST_MPL_AUX_NA_PARAM(T2) |
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> |
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struct if_ |
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{ |
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enum { msvc_wknd_ = BOOST_MPL_AUX_MSVC_VALUE_WKND(C_)::value }; |
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typedef typename aux::if_impl< BOOST_MPL_AUX_STATIC_CAST(bool, msvc_wknd_) > |
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::template result_<T1,T2>::type type; |
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BOOST_MPL_AUX_LAMBDA_SUPPORT(3,if_,(C_,T1,T2)) |
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}; |
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#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION |
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BOOST_MPL_AUX_NA_SPEC(3, if_) |
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}} |
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#endif // BOOST_MPL_IF_HPP_INCLUDED
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