Update of /cvsroot/boost/boost/boost/xpressive/proto/context
In directory
sc8-pr-cvs3.sourceforge.net:/tmp/cvs-serv20242/boost/xpressive/proto/context
Added Files:
null.hpp
Log Message:
add null_context, use in vector.cpp example
--- NEW FILE: null.hpp ---
#ifndef BOOST_PP_IS_ITERATING
///////////////////////////////////////////////////////////////////////////////
/// \file null.hpp
/// Definintion of null_context\<\>, an evaluation context for
/// proto::eval() that simply evaluates each child expression, doesn't
/// combine the results at all, and returns void.
//
// Copyright 2004 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_PROTO_CONTEXT_NULL_HPP_EAN_06_24_2007
#define BOOST_PROTO_CONTEXT_NULL_HPP_EAN_06_24_2007
#include <boost/xpressive/proto/detail/prefix.hpp> // must be first include
#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/repetition/repeat.hpp>
#include <boost/xpressive/proto/proto_fwd.hpp>
#include <boost/xpressive/proto/eval.hpp>
#include <boost/xpressive/proto/traits.hpp>
#include <boost/xpressive/proto/detail/suffix.hpp> // must be last include
namespace boost { namespace proto
{
template<typename Expr, typename Context, long Arity =
Expr::proto_arity::value>
struct null_eval
{};
template<typename Expr, typename Context>
struct null_eval<Expr, Context, 0>
{
typedef void result_type;
void operator()(Expr &, Context &) const
{}
};
#define BOOST_PROTO_EVAL_N(Z, N, DATA)
\
proto::eval(proto::arg_c<N>(expr), ctx);
\
/**/
#define BOOST_PP_ITERATION_PARAMS_1
\
(3, (1, BOOST_PROTO_MAX_ARITY,
<boost/xpressive/proto/context/null.hpp>)) \
/**/
#include BOOST_PP_ITERATE()
#undef BOOST_PROTO_EVAL_N
/// null_context
///
struct null_context
{
/// null_context::eval
///
template<typename Expr>
struct eval
: null_eval<Expr, null_context const>
{};
};
}}
#endif
#else
#define N BOOST_PP_ITERATION()
template<typename Expr, typename Context>
struct null_eval<Expr, Context, N>
{
typedef void result_type;
void operator ()(Expr &expr, Context &ctx) const
{
BOOST_PP_REPEAT(N, BOOST_PROTO_EVAL_N, ~)
}
};
#undef N
#endif
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