| #ifndef BOOST_PP_IS_ITERATING |
| /////////////////////////////////////////////////////////////////////////////// |
| /// \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> |
| |
| 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> |
| {}; |
| }; |
| |
| #define BOOST_PP_ITERATION_PARAMS_1 (3, (0, BOOST_PROTO_MAX_ARITY, <boost/proto/transform/lazy.hpp>)) |
| #include BOOST_PP_ITERATE() |
| |
| /// INTERNAL ONLY |
| /// |
| template<typename Object> |
| struct is_callable<lazy<Object> > |
| : mpl::true_ |
| {}; |
| |
| }} |
| |
| #endif |
| |
| #else |
| |
| #define N BOOST_PP_ITERATION() |
| |
| /// \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 BOOST_PP_ENUM_TRAILING_PARAMS(N, typename A)> |
| struct lazy<Object(BOOST_PP_ENUM_PARAMS(N, A))> |
| : transform<lazy<Object(BOOST_PP_ENUM_PARAMS(N, A))> > |
| { |
| template<typename Expr, typename State, typename Data> |
| struct impl |
| : call< |
| typename make<Object>::template impl<Expr, State, Data>::result_type |
| (BOOST_PP_ENUM_PARAMS(N, A)) |
| >::template impl<Expr, State, Data> |
| {}; |
| }; |
| |
| #undef N |
| |
| #endif |