136 lines
2.8 KiB
C++
136 lines
2.8 KiB
C++
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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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// $Id$
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// $Date$
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// $Revision$
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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 https://lists.boost.org/Archives/boost/2004/09/71383.php
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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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