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102 lines
2.6 KiB
102 lines
2.6 KiB
3 years ago
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#ifndef BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED
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#define BOOST_MPL_AUX_BEGIN_END_IMPL_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/begin_end_fwd.hpp>
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#include <boost/mpl/sequence_tag_fwd.hpp>
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#include <boost/mpl/void.hpp>
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#include <boost/mpl/eval_if.hpp>
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#include <boost/mpl/aux_/has_begin.hpp>
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#include <boost/mpl/aux_/na.hpp>
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#include <boost/mpl/aux_/traits_lambda_spec.hpp>
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#include <boost/mpl/aux_/config/eti.hpp>
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namespace boost { namespace mpl {
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namespace aux {
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template< typename Sequence >
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struct begin_type
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{
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typedef typename Sequence::begin type;
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};
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template< typename Sequence >
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struct end_type
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{
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typedef typename Sequence::end type;
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};
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}
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// default implementation; conrete sequences might override it by
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// specializing either the 'begin_impl/end_impl' or the primary
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// 'begin/end' templates
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template< typename Tag >
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struct begin_impl
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{
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template< typename Sequence > struct apply
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{
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typedef typename eval_if<aux::has_begin<Sequence, true_>,
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aux::begin_type<Sequence>, void_>::type type;
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};
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};
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template< typename Tag >
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struct end_impl
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{
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template< typename Sequence > struct apply
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{
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typedef typename eval_if<aux::has_begin<Sequence, true_>,
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aux::end_type<Sequence>, void_>::type type;
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};
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};
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// specialize 'begin_trait/end_trait' for two pre-defined tags
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# define AUX778076_IMPL_SPEC(name, tag, result) \
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template<> \
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struct name##_impl<tag> \
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{ \
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template< typename Sequence > struct apply \
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{ \
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typedef result type; \
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}; \
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}; \
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/**/
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// a sequence with nested 'begin/end' typedefs; just query them
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AUX778076_IMPL_SPEC(begin, nested_begin_end_tag, typename Sequence::begin)
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AUX778076_IMPL_SPEC(end, nested_begin_end_tag, typename Sequence::end)
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// if a type 'T' does not contain 'begin/end' or 'tag' members
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// and doesn't specialize either 'begin/end' or 'begin_impl/end_impl'
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// templates, then we end up here
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AUX778076_IMPL_SPEC(begin, non_sequence_tag, void_)
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AUX778076_IMPL_SPEC(end, non_sequence_tag, void_)
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AUX778076_IMPL_SPEC(begin, na, void_)
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AUX778076_IMPL_SPEC(end, na, void_)
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# undef AUX778076_IMPL_SPEC
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BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC_IMPL(1,begin_impl)
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BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC_IMPL(1,end_impl)
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}}
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#endif // BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED
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