Mercurial > hg > vamp-build-and-test
diff DEPENDENCIES/generic/include/boost/proto/context/callable.hpp @ 16:2665513ce2d3
Add boost headers
| author | Chris Cannam |
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| date | Tue, 05 Aug 2014 11:11:38 +0100 |
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| children |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/DEPENDENCIES/generic/include/boost/proto/context/callable.hpp Tue Aug 05 11:11:38 2014 +0100 @@ -0,0 +1,229 @@ +/////////////////////////////////////////////////////////////////////////////// +/// \file callable.hpp +/// Definintion of callable_context\<\>, an evaluation context for +/// proto::eval() that explodes each node and calls the derived context +/// type with the expressions constituents. If the derived context doesn't +/// have an overload that handles this node, fall back to some other +/// context. +// +// 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_CONTEXT_CALLABLE_HPP_EAN_06_23_2007 +#define BOOST_PROTO_CONTEXT_CALLABLE_HPP_EAN_06_23_2007 + +#include <boost/config.hpp> +#include <boost/detail/workaround.hpp> +#include <boost/preprocessor/cat.hpp> +#include <boost/preprocessor/iteration/iterate.hpp> +#include <boost/preprocessor/facilities/intercept.hpp> +#include <boost/preprocessor/repetition/repeat.hpp> +#include <boost/preprocessor/repetition/enum_params.hpp> +#include <boost/preprocessor/repetition/enum_trailing.hpp> +#include <boost/preprocessor/repetition/enum_trailing_params.hpp> +#include <boost/preprocessor/arithmetic/inc.hpp> +#include <boost/preprocessor/selection/max.hpp> +#include <boost/mpl/if.hpp> +#include <boost/mpl/bool.hpp> +#include <boost/utility/result_of.hpp> +#include <boost/type_traits/remove_cv.hpp> +#include <boost/proto/proto_fwd.hpp> +#include <boost/proto/traits.hpp> // for child_c + +namespace boost { namespace proto +{ + namespace detail + { + template<typename Context> + struct callable_context_wrapper + : remove_cv<Context>::type + { + callable_context_wrapper(); + typedef private_type_ fun_type(...); + operator fun_type *() const; + private: + callable_context_wrapper &operator =(callable_context_wrapper const &); + }; + + template<typename T> + yes_type check_is_expr_handled(T const &); + + no_type check_is_expr_handled(private_type_ const &); + + template<typename Expr, typename Context, long Arity = Expr::proto_arity_c> + struct is_expr_handled; + + template<typename Expr, typename Context> + struct is_expr_handled<Expr, Context, 0> + { + static callable_context_wrapper<Context> &sctx_; + static Expr &sexpr_; + static typename Expr::proto_tag &stag_; + + static const bool value = + sizeof(yes_type) == + sizeof( + detail::check_is_expr_handled( + (sctx_(stag_, proto::value(sexpr_)), 0) + ) + ); + + typedef mpl::bool_<value> type; + }; + } + + namespace context + { + /// \brief A BinaryFunction that accepts a Proto expression and a + /// callable context and calls the context with the expression tag + /// and children as arguments, effectively fanning the expression + /// out. + /// + /// <tt>callable_eval\<\></tt> requires that \c Context is a + /// PolymorphicFunctionObject that can be invoked with \c Expr's + /// tag and children as expressions, as follows: + /// + /// \code + /// context(Expr::proto_tag(), child_c<0>(expr), child_c<1>(expr), ...) + /// \endcode + template< + typename Expr + , typename Context + , long Arity // = Expr::proto_arity_c + > + struct callable_eval + {}; + + /// \brief A BinaryFunction that accepts a Proto expression and a + /// callable context and calls the context with the expression tag + /// and children as arguments, effectively fanning the expression + /// out. + /// + /// <tt>callable_eval\<\></tt> requires that \c Context is a + /// PolymorphicFunctionObject that can be invoked with \c Expr's + /// tag and children as expressions, as follows: + /// + /// \code + /// context(Expr::proto_tag(), value(expr)) + /// \endcode + template<typename Expr, typename Context> + struct callable_eval<Expr, Context, 0> + { + typedef typename proto::result_of::value<Expr const &>::type value_type; + + typedef + typename BOOST_PROTO_RESULT_OF< + Context(typename Expr::proto_tag, value_type) + >::type + result_type; + + /// \param expr The current expression + /// \param context The callable evaluation context + /// \return <tt>context(Expr::proto_tag(), value(expr))</tt> + result_type operator ()(Expr &expr, Context &context) const + { + return context(typename Expr::proto_tag(), proto::value(expr)); + } + }; + + /// \brief An evaluation context adaptor that makes authoring a + /// context a simple matter of writing function overloads, rather + /// then writing template specializations. + /// + /// <tt>callable_context\<\></tt> is a base class that implements + /// the context protocol by passing fanned-out expression nodes to + /// the derived context, making it easy to customize the handling + /// of expression types by writing function overloads. Only those + /// expression types needing special handling require explicit + /// handling. All others are dispatched to a user-specified + /// default context, \c DefaultCtx. + /// + /// <tt>callable_context\<\></tt> is defined simply as: + /// + /// \code + /// template<typename Context, typename DefaultCtx = default_context> + /// struct callable_context + /// { + /// template<typename Expr, typename ThisContext = Context> + /// struct eval + /// : mpl::if_< + /// is_expr_handled_<Expr, Context> // For exposition + /// , callable_eval<Expr, ThisContext> + /// , typename DefaultCtx::template eval<Expr, Context> + /// >::type + /// {}; + /// }; + /// \endcode + /// + /// The Boolean metafunction <tt>is_expr_handled_\<\></tt> uses + /// metaprogramming tricks to determine whether \c Context has + /// an overloaded function call operator that accepts the + /// fanned-out constituents of an expression of type \c Expr. + /// If so, the handling of the expression is dispatched to + /// <tt>callable_eval\<\></tt>. If not, it is dispatched to + /// the user-specified \c DefaultCtx. + /// + /// Below is an example of how to use <tt>callable_context\<\></tt>: + /// + /// \code + /// // An evaluation context that increments all + /// // integer terminals in-place. + /// struct increment_ints + /// : callable_context< + /// increment_ints const // derived context + /// , null_context const // fall-back context + /// > + /// { + /// typedef void result_type; + /// + /// // Handle int terminals here: + /// void operator()(proto::tag::terminal, int &i) const + /// { + /// ++i; + /// } + /// }; + /// \endcode + /// + /// With \c increment_ints, we can do the following: + /// + /// \code + /// literal<int> i = 0, j = 10; + /// proto::eval( i - j * 3.14, increment_ints() ); + /// + /// assert( i.get() == 1 && j.get() == 11 ); + /// \endcode + template< + typename Context + , typename DefaultCtx // = default_context + > + struct callable_context + { + /// A BinaryFunction that accepts an \c Expr and a + /// \c Context, and either fans out the expression and passes + /// it to the context, or else hands off the expression to + /// \c DefaultCtx. + /// + /// If \c Context is a PolymorphicFunctionObject such that + /// it can be invoked with the tag and children of \c Expr, + /// as <tt>ctx(Expr::proto_tag(), child_c\<0\>(expr), child_c\<1\>(expr)...)</tt>, + /// then <tt>eval\<Expr, ThisContext\></tt> inherits from + /// <tt>callable_eval\<Expr, ThisContext\></tt>. Otherwise, + /// <tt>eval\<Expr, ThisContext\></tt> inherits from + /// <tt>DefaultCtx::eval\<Expr, Context\></tt>. + template<typename Expr, typename ThisContext = Context> + struct eval + : mpl::if_c< + detail::is_expr_handled<Expr, Context>::value + , callable_eval<Expr, ThisContext> + , typename DefaultCtx::template eval<Expr, Context> + >::type + {}; + }; + } + + #include <boost/proto/context/detail/callable_eval.hpp> + +}} + +#endif