Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: /// \file lazy.hpp
Chris@16: /// Contains definition of the lazy<> transform.
Chris@16: //
Chris@16: //  Copyright 2008 Eric Niebler. Distributed under the Boost
Chris@16: //  Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_PROTO_TRANSFORM_LAZY_HPP_EAN_12_02_2007
Chris@16: #define BOOST_PROTO_TRANSFORM_LAZY_HPP_EAN_12_02_2007
Chris@16: 
Chris@16: #include <boost/preprocessor/iteration/iterate.hpp>
Chris@16: #include <boost/preprocessor/repetition/enum_params.hpp>
Chris@16: #include <boost/preprocessor/repetition/enum_trailing_params.hpp>
Chris@16: #include <boost/proto/proto_fwd.hpp>
Chris@16: #include <boost/proto/transform/make.hpp>
Chris@16: #include <boost/proto/transform/call.hpp>
Chris@16: #include <boost/proto/transform/impl.hpp>
Chris@16: #include <boost/proto/transform/detail/pack.hpp>
Chris@16: 
Chris@16: namespace boost { namespace proto
Chris@16: {
Chris@16:     /// \brief A PrimitiveTransform that uses <tt>make\<\></tt> to build
Chris@16:     /// a CallableTransform, and then uses <tt>call\<\></tt> to apply it.
Chris@16:     ///
Chris@16:     /// <tt>lazy\<\></tt> is useful as a higher-order transform, when the
Chris@16:     /// transform to be applied depends on the current state of the
Chris@16:     /// transformation. The invocation of the <tt>make\<\></tt> transform
Chris@16:     /// evaluates any nested transforms, and the resulting type is treated
Chris@16:     /// as a CallableTransform, which is evaluated with <tt>call\<\></tt>.
Chris@16:     template<typename Object>
Chris@16:     struct lazy : transform<lazy<Object> >
Chris@16:     {
Chris@16:         template<typename Expr, typename State, typename Data>
Chris@16:         struct impl
Chris@16:           : call<
Chris@16:                 typename make<Object>::template impl<Expr, State, Data>::result_type
Chris@16:             >::template impl<Expr, State, Data>
Chris@16:         {};
Chris@16:     };
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     template<typename Fun>
Chris@16:     struct lazy<detail::msvc_fun_workaround<Fun> >
Chris@16:       : lazy<Fun>
Chris@16:     {};
Chris@16: 
Chris@16:     #include <boost/proto/transform/detail/lazy.hpp>
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<typename Object>
Chris@16:     struct is_callable<lazy<Object> >
Chris@16:       : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16: }}
Chris@16: 
Chris@16: #endif