boost/xpressive/detail/static/transforms/as_modifier.hpp
///////////////////////////////////////////////////////////////////////////////
// as_modifier.hpp
//
// Copyright 2007 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_MODIFIER_HPP_EAN_04_05_2007
#define BOOST_XPRESSIVE_DETAIL_STATIC_TRANSFORMS_AS_MODIFIER_HPP_EAN_04_05_2007
// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif
#include <boost/mpl/sizeof.hpp>
#include <boost/xpressive/detail/detail_fwd.hpp>
#include <boost/xpressive/detail/static/static.hpp>
#include <boost/xpressive/proto/proto.hpp>
#include <boost/xpressive/proto/transform/arg.hpp>
namespace boost { namespace xpressive { namespace detail
{
///////////////////////////////////////////////////////////////////////////////
// regex operator tags
struct modifier_tag
{
};
///////////////////////////////////////////////////////////////////////////////
// scoped_swap
// for swapping state back after proto::compile returns
template<typename Old, typename New>
struct scoped_swap
{
~scoped_swap() { this->old_->swap(*this->new_); }
Old *old_;
New *new_;
};
///////////////////////////////////////////////////////////////////////////////
// as_modifier
template<typename Grammar>
struct as_modifier
: Grammar
{
as_modifier();
template<typename Expr, typename State, typename Visitor>
struct apply
{
typedef typename proto::result_of::arg<typename proto::result_of::left<Expr>::type>::type modifier_type;
typedef typename modifier_type::BOOST_NESTED_TEMPLATE apply<Visitor>::type visitor_type;
typedef typename proto::transform::right<Grammar>::template apply<Expr, State, visitor_type>::type type;
};
template<typename Expr, typename State, typename Visitor>
static typename apply<Expr, State, Visitor>::type
call(Expr const &expr, State const &state, Visitor &visitor)
{
typedef typename apply<Expr, State, Visitor>::visitor_type new_visitor_type;
new_visitor_type new_visitor(proto::arg(proto::left(expr)).call(visitor));
new_visitor.swap(visitor);
scoped_swap<Visitor, new_visitor_type> const undo = {&visitor, &new_visitor};
detail::ignore_unused(undo);
return proto::transform::right<Grammar>::call(expr, state, new_visitor);
}
};
}}}
#endif