285 lines
9.7 KiB
C++
285 lines
9.7 KiB
C++
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///////////////////////////////////////////////////////////////////////////////
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/// \file make.hpp
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/// Contains definition of the make<> 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_MAKE_HPP_EAN_12_02_2007
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#define BOOST_PROTO_TRANSFORM_MAKE_HPP_EAN_12_02_2007
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#include <boost/detail/workaround.hpp>
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#include <boost/preprocessor/repetition/enum.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/preprocessor/repetition/enum_binary_params.hpp>
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#include <boost/preprocessor/repetition/enum_params_with_a_default.hpp>
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#include <boost/preprocessor/repetition/repeat_from_to.hpp>
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#include <boost/preprocessor/facilities/intercept.hpp>
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#include <boost/preprocessor/cat.hpp>
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#include <boost/preprocessor/iteration/iterate.hpp>
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#include <boost/preprocessor/selection/max.hpp>
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#include <boost/preprocessor/arithmetic/inc.hpp>
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#include <boost/mpl/and.hpp>
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#include <boost/mpl/aux_/has_type.hpp>
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#include <boost/proto/detail/template_arity.hpp>
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#include <boost/utility/result_of.hpp>
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#include <boost/proto/proto_fwd.hpp>
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#include <boost/proto/traits.hpp>
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#include <boost/proto/args.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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#include <boost/proto/detail/as_lvalue.hpp>
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#include <boost/proto/detail/ignore_unused.hpp>
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#if defined(_MSC_VER)
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# pragma warning(push)
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# pragma warning(disable : 4714) // function 'xxx' marked as __forceinline not inlined
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#endif
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namespace boost { namespace proto
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{
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namespace detail
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{
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template<typename T>
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struct is_applyable
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: mpl::and_<is_callable<T>, is_transform<T> >
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{};
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template<typename T, bool HasType = mpl::aux::has_type<T>::value>
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struct nested_type
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{
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typedef typename T::type type;
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};
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template<typename T>
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struct nested_type<T, false>
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{
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typedef T type;
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};
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template<typename T, bool Applied>
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struct nested_type_if
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{
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typedef T type;
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static bool const applied = false;
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};
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template<typename T>
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struct nested_type_if<T, true>
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: nested_type<T>
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{
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static bool const applied = true;
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};
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template<
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typename R
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, typename Expr, typename State, typename Data
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BOOST_PROTO_TEMPLATE_ARITY_PARAM(long Arity = detail::template_arity<R>::value)
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>
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struct make_
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{
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typedef R type;
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static bool const applied = false;
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};
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template<
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typename R
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, typename Expr, typename State, typename Data
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, bool IsApplyable = is_applyable<R>::value
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>
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struct make_if_
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: make_<R, Expr, State, Data>
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{};
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template<typename R, typename Expr, typename State, typename Data>
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struct make_if_<R, Expr, State, Data, true>
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: uncvref<typename when<_, R>::template impl<Expr, State, Data>::result_type>
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{
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static bool const applied = true;
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};
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#if BOOST_WORKAROUND(__GNUC__, == 3) || (BOOST_WORKAROUND(__GNUC__, == 4) && __GNUC_MINOR__ == 0)
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// work around GCC bug
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template<typename Tag, typename Args, long N, typename Expr, typename State, typename Data>
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struct make_if_<proto::expr<Tag, Args, N>, Expr, State, Data, false>
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{
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typedef proto::expr<Tag, Args, N> type;
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static bool const applied = false;
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};
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// work around GCC bug
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template<typename Tag, typename Args, long N, typename Expr, typename State, typename Data>
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struct make_if_<proto::basic_expr<Tag, Args, N>, Expr, State, Data, false>
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{
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typedef proto::basic_expr<Tag, Args, N> type;
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static bool const applied = false;
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};
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#endif
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template<typename Type, bool IsAggregate = detail::is_aggregate_<Type>::value>
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struct construct_
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{
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typedef Type result_type;
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BOOST_FORCEINLINE
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Type operator ()() const
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{
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return Type();
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}
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// Other overloads generated by the preprocessor
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#include <boost/proto/transform/detail/construct_funop.hpp>
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};
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template<typename Type>
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struct construct_<Type, true>
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{
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typedef Type result_type;
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BOOST_FORCEINLINE
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Type operator ()() const
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{
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return Type();
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}
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// Other overloads generated by the preprocessor
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#include <boost/proto/transform/detail/construct_pod_funop.hpp>
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};
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}
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/// \brief A PrimitiveTransform which prevents another PrimitiveTransform
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/// from being applied in an \c ObjectTransform.
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///
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/// When building higher order transforms with <tt>make\<\></tt> or
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/// <tt>lazy\<\></tt>, you sometimes would like to build types that
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/// are parameterized with Proto transforms. In such lambda-style
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/// transforms, Proto will unhelpfully find all nested transforms
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/// and apply them, even if you don't want them to be applied. Consider
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/// the following transform, which will replace the \c _ in
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/// <tt>Bar<_>()</tt> with <tt>proto::terminal\<int\>::type</tt>:
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///
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/// \code
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/// template<typename T>
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/// struct Bar
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/// {};
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///
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/// struct Foo
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/// : proto::when<_, Bar<_>() >
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/// {};
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///
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/// proto::terminal<int>::type i = {0};
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///
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/// int main()
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/// {
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/// Foo()(i);
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/// std::cout << typeid(Foo()(i)).name() << std::endl;
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/// }
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/// \endcode
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///
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/// If you actually wanted to default-construct an object of type
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/// <tt>Bar\<_\></tt>, you would have to protect the \c _ to prevent
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/// it from being applied. You can use <tt>proto::protect\<\></tt>
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/// as follows:
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///
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/// \code
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/// // OK: replace anything with Bar<_>()
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/// struct Foo
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/// : proto::when<_, Bar<protect<_> >() >
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/// {};
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/// \endcode
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template<typename PrimitiveTransform>
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struct protect : transform<protect<PrimitiveTransform> >
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{
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template<typename, typename, typename>
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struct impl
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{
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typedef PrimitiveTransform result_type;
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};
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};
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/// \brief A PrimitiveTransform which computes a type by evaluating any
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/// nested transforms and then constructs an object of that type.
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///
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/// The <tt>make\<\></tt> transform checks to see if \c Object is a template.
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/// If it is, the template type is disassembled to find nested transforms.
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/// Proto considers the following types to represent transforms:
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///
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/// \li Function types
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/// \li Function pointer types
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/// \li Types for which <tt>proto::is_callable\< type \>::value</tt> is \c true
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///
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/// <tt>boost::result_of\<make\<T\<X0,X1,...\> \>(Expr, State, Data)\>::type</tt>
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/// is evaluated as follows. For each \c X in <tt>X0,X1,...</tt>, do:
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///
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/// \li If \c X is a template like <tt>U\<Y0,Y1,...\></tt>, then let <tt>X'</tt>
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/// be <tt>boost::result_of\<make\<U\<Y0,Y1,...\> \>(Expr, State, Data)\>::type</tt>
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/// (which evaluates this procedure recursively). Note whether any
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/// substitutions took place during this operation.
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/// \li Otherwise, if \c X is a transform, then let <tt>X'</tt> be
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/// <tt>boost::result_of\<when\<_, X\>(Expr, State, Data)\>::type</tt>.
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/// Note that a substitution took place.
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/// \li Otherwise, let <tt>X'</tt> be \c X, and note that no substitution
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/// took place.
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/// \li If any substitutions took place in any of the above steps and
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/// <tt>T\<X0',X1',...\></tt> has a nested <tt>::type</tt> typedef,
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/// the result type is <tt>T\<X0',X1',...\>::type</tt>.
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/// \li Otherwise, the result type is <tt>T\<X0',X1',...\></tt>.
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///
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/// Note that <tt>when\<\></tt> is implemented in terms of <tt>call\<\></tt>
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/// and <tt>make\<\></tt>, so the above procedure is evaluated recursively.
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template<typename Object>
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struct make : transform<make<Object> >
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{
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template<typename Expr, typename State, typename Data>
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struct impl : transform_impl<Expr, State, Data>
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{
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typedef typename detail::make_if_<Object, Expr, State, Data>::type result_type;
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/// \return <tt>result_type()</tt>
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BOOST_FORCEINLINE
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result_type operator ()(
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typename impl::expr_param
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, typename impl::state_param
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, typename impl::data_param
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) const
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{
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return result_type();
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}
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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 make<detail::msvc_fun_workaround<Fun> >
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: make<Fun>
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{};
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// Other specializations generated by the preprocessor.
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#include <boost/proto/transform/detail/make.hpp>
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#include <boost/proto/transform/detail/make_gcc_workaround.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<make<Object> >
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: mpl::true_
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{};
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/// INTERNAL ONLY
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///
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template<typename PrimitiveTransform>
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struct is_callable<protect<PrimitiveTransform> >
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: mpl::true_
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{};
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}}
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#if defined(_MSC_VER)
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# pragma warning(pop)
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#endif
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#endif
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