60 lines
2.1 KiB
C++
60 lines
2.1 KiB
C++
|
///////////////////////////////////////////////////////////////////////////////
|
||
|
|
/// \file lazy.hpp
|
||
|
|
/// Contains definition of the lazy<> transform.
|
||
|
|
//
|
||
|
|
// 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_TRANSFORM_LAZY_HPP_EAN_12_02_2007
|
||
|
|
#define BOOST_PROTO_TRANSFORM_LAZY_HPP_EAN_12_02_2007
|
||
|
|
|
||
|
|
#include <boost/preprocessor/iteration/iterate.hpp>
|
||
|
|
#include <boost/preprocessor/repetition/enum_params.hpp>
|
||
|
|
#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
|
||
|
|
#include <boost/proto/proto_fwd.hpp>
|
||
|
|
#include <boost/proto/transform/make.hpp>
|
||
|
|
#include <boost/proto/transform/call.hpp>
|
||
|
|
#include <boost/proto/transform/impl.hpp>
|
||
|
|
#include <boost/proto/transform/detail/pack.hpp>
|
||
|
|
|
||
|
|
namespace boost { namespace proto
|
||
|
|
{
|
||
|
|
/// \brief A PrimitiveTransform that uses <tt>make\<\></tt> to build
|
||
|
|
/// a CallableTransform, and then uses <tt>call\<\></tt> to apply it.
|
||
|
|
///
|
||
|
|
/// <tt>lazy\<\></tt> is useful as a higher-order transform, when the
|
||
|
|
/// transform to be applied depends on the current state of the
|
||
|
|
/// transformation. The invocation of the <tt>make\<\></tt> transform
|
||
|
|
/// evaluates any nested transforms, and the resulting type is treated
|
||
|
|
/// as a CallableTransform, which is evaluated with <tt>call\<\></tt>.
|
||
|
|
template<typename Object>
|
||
|
|
struct lazy : transform<lazy<Object> >
|
||
|
|
{
|
||
|
|
template<typename Expr, typename State, typename Data>
|
||
|
|
struct impl
|
||
|
|
: call<
|
||
|
|
typename make<Object>::template impl<Expr, State, Data>::result_type
|
||
|
|
>::template impl<Expr, State, Data>
|
||
|
|
{};
|
||
|
|
};
|
||
|
|
|
||
|
|
/// INTERNAL ONLY
|
||
|
|
template<typename Fun>
|
||
|
|
struct lazy<detail::msvc_fun_workaround<Fun> >
|
||
|
|
: lazy<Fun>
|
||
|
|
{};
|
||
|
|
|
||
|
|
#include <boost/proto/transform/detail/lazy.hpp>
|
||
|
|
|
||
|
|
/// INTERNAL ONLY
|
||
|
|
///
|
||
|
|
template<typename Object>
|
||
|
|
struct is_callable<lazy<Object> >
|
||
|
|
: mpl::true_
|
||
|
|
{};
|
||
|
|
|
||
|
|
}}
|
||
|
|
|
||
|
|
#endif
|