57 lines
1.6 KiB
C++
57 lines
1.6 KiB
C++
///////////////////////////////////////////////////////////////////////////////
|
|
/// \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 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_PROTO_CONTEXT_NULL_HPP_EAN_06_24_2007
|
|
#define BOOST_PROTO_CONTEXT_NULL_HPP_EAN_06_24_2007
|
|
|
|
#include <boost/preprocessor/iteration/iterate.hpp>
|
|
#include <boost/preprocessor/repetition/repeat.hpp>
|
|
#include <boost/proto/proto_fwd.hpp>
|
|
#include <boost/proto/eval.hpp>
|
|
#include <boost/proto/traits.hpp>
|
|
|
|
namespace boost { namespace proto { namespace context
|
|
{
|
|
|
|
template<
|
|
typename Expr
|
|
, typename Context
|
|
, long Arity // = Expr::proto_arity_c
|
|
>
|
|
struct null_eval
|
|
{};
|
|
|
|
template<typename Expr, typename Context>
|
|
struct null_eval<Expr, Context, 0>
|
|
{
|
|
typedef void result_type;
|
|
void operator()(Expr &, Context &) const
|
|
{}
|
|
};
|
|
|
|
// Additional specializations generated by the preprocessor
|
|
#include <boost/proto/context/detail/null_eval.hpp>
|
|
|
|
/// null_context
|
|
///
|
|
struct null_context
|
|
{
|
|
/// null_context::eval
|
|
///
|
|
template<typename Expr, typename ThisContext = null_context const>
|
|
struct eval
|
|
: null_eval<Expr, ThisContext>
|
|
{};
|
|
};
|
|
|
|
}}}
|
|
|
|
#endif
|