49 lines
2.0 KiB
Plaintext
49 lines
2.0 KiB
Plaintext
// Boost.Range library
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//
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// Copyright Arno Schoedl & Neil Groves 2009.
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// Use, modification and distribution is subject to the Boost Software
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// License, Version 1.0. (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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// For more information, see http://www.boost.org/libs/range/
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//
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#ifndef BOOST_RANGE_DETAIL_EXTRACT_OPTIONAL_TYPE_HPP_INCLUDED
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#define BOOST_RANGE_DETAIL_EXTRACT_OPTIONAL_TYPE_HPP_INCLUDED
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#if defined(_MSC_VER)
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# pragma once
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#endif
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#include <boost/config.hpp>
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#include <boost/preprocessor/cat.hpp>
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#include <boost/mpl/has_xxx.hpp>
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#if !defined(BOOST_MPL_CFG_NO_HAS_XXX)
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// Defines extract_some_typedef<T> which exposes T::some_typedef as
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// extract_some_typedef<T>::type if T::some_typedef exists. Otherwise
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// extract_some_typedef<T> is empty.
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#define BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( a_typedef ) \
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BOOST_MPL_HAS_XXX_TRAIT_DEF(a_typedef) \
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template< typename C, bool B = BOOST_PP_CAT(has_, a_typedef)<C>::value > \
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struct BOOST_PP_CAT(extract_, a_typedef) \
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{}; \
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template< typename C > \
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struct BOOST_PP_CAT(extract_, a_typedef)< C, true > \
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{ \
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typedef BOOST_DEDUCED_TYPENAME C::a_typedef type; \
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};
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#else
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#define BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( a_typedef ) \
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template< typename C > \
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struct BOOST_PP_CAT(extract_, a_typedef) \
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{ \
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typedef BOOST_DEDUCED_TYPENAME C::a_typedef type; \
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};
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#endif
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#endif // include guard
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