boost/proto/generate.hpp
/////////////////////////////////////////////////////////////////////////////// /// \file generate.hpp /// Contains definition of generate\<\> class template, which end users can /// specialize for generating domain-specific expression wrappers. // // 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_GENERATE_HPP_EAN_02_13_2007 #define BOOST_PROTO_GENERATE_HPP_EAN_02_13_2007 #include <boost/config.hpp> #include <boost/version.hpp> #include <boost/preprocessor/cat.hpp> #include <boost/preprocessor/iteration/iterate.hpp> #include <boost/preprocessor/facilities/intercept.hpp> #include <boost/preprocessor/repetition/enum_params.hpp> #include <boost/preprocessor/repetition/enum_binary_params.hpp> #include <boost/preprocessor/repetition/enum_trailing_params.hpp> #include <boost/mpl/bool.hpp> #include <boost/utility/enable_if.hpp> #include <boost/utility/result_of.hpp> #include <boost/proto/proto_fwd.hpp> #include <boost/proto/args.hpp> namespace boost { namespace proto { namespace detail { template<typename Expr> struct by_value_generator_; template<typename Tag, typename Arg> struct by_value_generator_<proto::expr<Tag, term<Arg>, 0> > { typedef proto::expr< Tag , term<typename detail::term_traits<Arg>::value_type> , 0 > type; static type const call(proto::expr<Tag, term<Arg>, 0> const &e) { type that = {e.child0}; return that; } }; template<typename Tag, typename Arg> struct by_value_generator_<proto::basic_expr<Tag, term<Arg>, 0> > { typedef proto::basic_expr< Tag , term<typename detail::term_traits<Arg>::value_type> , 0 > type; static type const call(proto::basic_expr<Tag, term<Arg>, 0> const &e) { type that = {e.child0}; return that; } }; // Include the other specializations of by_value_generator_ #include <boost/proto/detail/generate_by_value.hpp> } /// \brief Annotate a generator to indicate that it would /// prefer to be passed instances of \c proto::basic_expr\<\> rather /// than \c proto::expr\<\>. <tt>use_basic_expr\<Generator\></tt> is /// itself a generator. /// template<typename Generator> struct use_basic_expr : Generator { BOOST_PROTO_USE_BASIC_EXPR() }; /// \brief A simple generator that passes an expression /// through unchanged. /// /// Generators are intended for use as the first template parameter /// to the \c domain\<\> class template and control if and how /// expressions within that domain are to be customized. /// The \c default_generator makes no modifications to the expressions /// passed to it. struct default_generator { BOOST_PROTO_CALLABLE() template<typename Sig> struct result; template<typename This, typename Expr> struct result<This(Expr)> { typedef Expr type; }; /// \param expr A Proto expression /// \return expr template<typename Expr> #ifdef BOOST_PROTO_STRICT_RESULT_OF Expr #else Expr const & #endif operator ()(Expr const &e) const { return e; } }; /// \brief A simple generator that passes an expression /// through unchanged and specifies a preference for /// \c proto::basic_expr\<\> over \c proto::expr\<\>. /// /// Generators are intended for use as the first template parameter /// to the \c domain\<\> class template and control if and how /// expressions within that domain are to be customized. /// The \c default_generator makes no modifications to the expressions /// passed to it. struct basic_default_generator : proto::use_basic_expr<default_generator> {}; /// \brief A generator that wraps expressions passed /// to it in the specified extension wrapper. /// /// Generators are intended for use as the first template parameter /// to the \c domain\<\> class template and control if and how /// expressions within that domain are to be customized. /// \c generator\<\> wraps each expression passed to it in /// the \c Extends\<\> wrapper. template<template<typename> class Extends> struct generator { BOOST_PROTO_CALLABLE() BOOST_PROTO_USE_BASIC_EXPR() template<typename Sig> struct result; template<typename This, typename Expr> struct result<This(Expr)> { typedef Extends<Expr> type; }; template<typename This, typename Expr> struct result<This(Expr &)> { typedef Extends<Expr> type; }; template<typename This, typename Expr> struct result<This(Expr const &)> { typedef Extends<Expr> type; }; /// \param expr A Proto expression /// \return Extends<Expr>(expr) template<typename Expr> Extends<Expr> operator ()(Expr const &e) const { return Extends<Expr>(e); } }; /// \brief A generator that wraps expressions passed /// to it in the specified extension wrapper and uses /// aggregate initialization for the wrapper. /// /// Generators are intended for use as the first template parameter /// to the \c domain\<\> class template and control if and how /// expressions within that domain are to be customized. /// \c pod_generator\<\> wraps each expression passed to it in /// the \c Extends\<\> wrapper, and uses aggregate initialzation /// for the wrapped object. template<template<typename> class Extends> struct pod_generator { BOOST_PROTO_CALLABLE() BOOST_PROTO_USE_BASIC_EXPR() template<typename Sig> struct result; template<typename This, typename Expr> struct result<This(Expr)> { typedef Extends<Expr> type; }; template<typename This, typename Expr> struct result<This(Expr &)> { typedef Extends<Expr> type; }; template<typename This, typename Expr> struct result<This(Expr const &)> { typedef Extends<Expr> type; }; /// \param expr The expression to wrap /// \return <tt>Extends\<Expr\> that = {expr}; return that;</tt> template<typename Expr> Extends<Expr> operator ()(Expr const &e) const { Extends<Expr> that = {e}; return that; } }; /// \brief A generator that replaces child nodes held by /// reference with ones held by value. Use with /// \c compose_generators to forward that result to another /// generator. /// /// Generators are intended for use as the first template parameter /// to the \c domain\<\> class template and control if and how /// expressions within that domain are to be customized. /// \c by_value_generator ensures all child nodes are /// held by value. This generator is typically composed with a /// second generator for further processing, as /// <tt>compose_generators\<by_value_generator, MyGenerator\></tt>. struct by_value_generator { BOOST_PROTO_CALLABLE() template<typename Sig> struct result; template<typename This, typename Expr> struct result<This(Expr)> { typedef typename detail::by_value_generator_<Expr>::type type; }; template<typename This, typename Expr> struct result<This(Expr &)> { typedef typename detail::by_value_generator_<Expr>::type type; }; template<typename This, typename Expr> struct result<This(Expr const &)> { typedef typename detail::by_value_generator_<Expr>::type type; }; /// \param expr The expression to modify. /// \return <tt>deep_copy(expr)</tt> template<typename Expr> typename result<by_value_generator(Expr)>::type operator ()(Expr const &e) const { return detail::by_value_generator_<Expr>::call(e); } }; /// \brief A composite generator that first applies one /// transform to an expression and then forwards the result /// on to another generator for further transformation. /// /// Generators are intended for use as the first template parameter /// to the \c domain\<\> class template and control if and how /// expressions within that domain are to be customized. /// \c compose_generators\<\> is a composite generator that first /// applies one transform to an expression and then forwards the /// result on to another generator for further transformation. template<typename First, typename Second> struct compose_generators { BOOST_PROTO_CALLABLE() template<typename Sig> struct result; template<typename This, typename Expr> struct result<This(Expr)> { typedef typename Second::template result< Second(typename First::template result<First(Expr)>::type) >::type type; }; template<typename This, typename Expr> struct result<This(Expr &)> { typedef typename Second::template result< Second(typename First::template result<First(Expr)>::type) >::type type; }; template<typename This, typename Expr> struct result<This(Expr const &)> { typedef typename Second::template result< Second(typename First::template result<First(Expr)>::type) >::type type; }; /// \param expr The expression to modify. /// \return Second()(First()(expr)) template<typename Expr> typename result<compose_generators(Expr)>::type operator ()(Expr const &e) const { return Second()(First()(e)); } }; /// \brief Tests a generator to see whether it would prefer /// to be passed instances of \c proto::basic_expr\<\> rather than /// \c proto::expr\<\>. /// template<typename Generator, typename Void> struct wants_basic_expr : mpl::false_ {}; template<typename Generator> struct wants_basic_expr<Generator, typename Generator::proto_use_basic_expr_> : mpl::true_ {}; /// INTERNAL ONLY template<> struct is_callable<default_generator> : mpl::true_ {}; /// INTERNAL ONLY template<template<typename> class Extends> struct is_callable<generator<Extends> > : mpl::true_ {}; /// INTERNAL ONLY template<template<typename> class Extends> struct is_callable<pod_generator<Extends> > : mpl::true_ {}; /// INTERNAL ONLY template<> struct is_callable<by_value_generator> : mpl::true_ {}; /// INTERNAL ONLY template<typename First, typename Second> struct is_callable<compose_generators<First, Second> > : mpl::true_ {}; }} // Specializations of boost::result_of and boost::tr1_result_of to eliminate // some unnecessary template instantiations namespace boost { template<typename Expr> struct result_of<proto::default_domain(Expr)> { typedef Expr type; }; template<typename Expr> struct result_of<proto::basic_default_domain(Expr)> { typedef Expr type; }; template<typename Expr> struct result_of<proto::default_generator(Expr)> { typedef Expr type; }; template<typename Expr> struct result_of<proto::basic_default_generator(Expr)> { typedef Expr type; }; #if BOOST_VERSION >= 104400 template<typename Expr> struct tr1_result_of<proto::default_domain(Expr)> { typedef Expr type; }; template<typename Expr> struct tr1_result_of<proto::basic_default_domain(Expr)> { typedef Expr type; }; template<typename Expr> struct tr1_result_of<proto::default_generator(Expr)> { typedef Expr type; }; template<typename Expr> struct tr1_result_of<proto::basic_default_generator(Expr)> { typedef Expr type; }; #endif } #endif // BOOST_PROTO_GENERATE_HPP_EAN_02_13_2007