60 lines
2.1 KiB
Plaintext
60 lines
2.1 KiB
Plaintext
///////////////////////////////////////////////////////////////////////////////
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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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#include <boost/proto/transform/detail/pack.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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/// INTERNAL ONLY
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template<typename Fun>
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struct lazy<detail::msvc_fun_workaround<Fun> >
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: lazy<Fun>
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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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