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///////////////////////////////////////////////////////////////////////////////
// as_alternate.hpp
//
// Copyright 2008 Eric Niebler. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_ALTERNATE_HPP_EAN_04_01_2007
#define BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_ALTERNATE_HPP_EAN_04_01_2007
// MS compatible compilers support #pragma once
#if defined(_MSC_VER)
# pragma once
#endif
#include <boost/config.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/proto/core.hpp>
#include <boost/xpressive/detail/detail_fwd.hpp>
#include <boost/xpressive/detail/static/static.hpp>
#include <boost/xpressive/detail/core/matcher/alternate_matcher.hpp>
#include <boost/xpressive/detail/utility/cons.hpp>
namespace boost { namespace xpressive
{
namespace detail
{
///////////////////////////////////////////////////////////////////////////////
// alternates_list
// a fusion-compatible sequence of alternate expressions, that also keeps
// track of the list's width and purity.
template<typename Head, typename Tail>
struct alternates_list
: fusion::cons<Head, Tail>
{
BOOST_STATIC_CONSTANT(std::size_t, width = Head::width == Tail::width ? Head::width : detail::unknown_width::value);
BOOST_STATIC_CONSTANT(bool, pure = Head::pure && Tail::pure);
alternates_list(Head const &head, Tail const &tail)
: fusion::cons<Head, Tail>(head, tail)
{
}
};
template<typename Head>
struct alternates_list<Head, fusion::nil>
: fusion::cons<Head, fusion::nil>
{
BOOST_STATIC_CONSTANT(std::size_t, width = Head::width);
BOOST_STATIC_CONSTANT(bool, pure = Head::pure);
alternates_list(Head const &head, fusion::nil const &tail)
: fusion::cons<Head, fusion::nil>(head, tail)
{
}
};
}
namespace grammar_detail
{
///////////////////////////////////////////////////////////////////////////////
// in_alternate_list
template<typename Grammar, typename Callable = proto::callable>
struct in_alternate_list : proto::transform<in_alternate_list<Grammar, Callable> >
{
template<typename Expr, typename State, typename Data>
struct impl : proto::transform_impl<Expr, State, Data>
{
typedef
detail::alternates_list<
typename Grammar::template impl<
Expr
, detail::alternate_end_xpression
, Data
>::result_type
, State
>
result_type;
result_type operator ()(
typename impl::expr_param expr
, typename impl::state_param state
, typename impl::data_param data
) const
{
return result_type(
typename Grammar::template impl<Expr, detail::alternate_end_xpression, Data>()(
expr
, detail::alternate_end_xpression()
, data
)
, state
);
}
};
};
///////////////////////////////////////////////////////////////////////////////
// as_alternate_matcher
template<typename Grammar, typename Callable = proto::callable>
struct as_alternate_matcher : proto::transform<as_alternate_matcher<Grammar, Callable> >
{
template<typename Expr, typename State, typename Data>
struct impl : proto::transform_impl<Expr, State, Data>
{
typedef typename impl::data data_type;
typedef
detail::alternate_matcher<
typename Grammar::template impl<Expr, State, Data>::result_type
, typename data_type::traits_type
>
result_type;
result_type operator ()(
typename impl::expr_param expr
, typename impl::state_param state
, typename impl::data_param data
) const
{
return result_type(
typename Grammar::template impl<Expr, State, Data>()(expr, state, data)
);
}
};
};
}
}}
#endif
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