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