begin_end_impl.hpp

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//-----------------------------------------------------------------------------
// boost mpl/aux_/begin_end_impl.hpp header file
// See http://www.boost.org for updates, documentation, and revision history.
//-----------------------------------------------------------------------------
//
// Copyright (c) 2000-02
// Aleksey Gurtovoy
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee, 
// provided that the above copyright notice appears in all copies and 
// that both the copyright notice and this permission notice appear in 
// supporting documentation. No representations are made about the 
// suitability of this software for any purpose. It is provided "as is" 
// without express or implied warranty.

#ifndef BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED
#define BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED

#include "boost/mpl/begin_end_fwd.hpp"
#include "boost/mpl/sequence_tag_fwd.hpp"
#include "boost/mpl/void.hpp"
#include "boost/mpl/aux_/traits_lambda_spec.hpp"
#include "boost/mpl/aux_/config/eti.hpp"

namespace boost {
namespace mpl {

// default implementation; conrete sequences might override it by 
// specializing either the 'begin_traits/end_traits' or the primary 
// 'begin/end' templates

template< typename Tag >
struct begin_traits
{
    template< typename Sequence > struct algorithm
    {
        typedef typename Sequence::begin type;
    };
};

template< typename Tag >
struct end_traits
{
    template< typename Sequence > struct algorithm
    {
        typedef typename Sequence::end type;
    };
};

// specialize 'begin_trait/end_trait' for two pre-defined tags

#   define AUX_AGLORITM_TRAIT_SPEC(name, tag, result) \
template<> \
struct name##_traits<tag> \
{ \
    template< typename Sequence > struct algorithm  \
    { \
        typedef result type; \
    }; \
}; \
/**/

// a sequence with nested 'begin/end' typedefs; just query them
AUX_AGLORITM_TRAIT_SPEC(begin, nested_begin_end_tag, typename Sequence::begin)
AUX_AGLORITM_TRAIT_SPEC(end, nested_begin_end_tag, typename Sequence::end)

// if a type 'T' does not contain 'begin/end' or 'tag' members 
// and doesn't specialize either 'begin/end' or 'begin_traits/end_traits' 
// templates, then we end up here
AUX_AGLORITM_TRAIT_SPEC(begin, non_sequence_tag, void_)
AUX_AGLORITM_TRAIT_SPEC(end, non_sequence_tag, void_)

#   undef AUX_AGLORITM_TRAIT_SPEC


BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC(1,begin_traits)
BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC(1,end_traits)

} // namespace mpl
} // namespace boost

#endif // BOOST_MPL_AUX_BEGIN_END_IMPL_HPP_INCLUDED