boost/proto/generate.hpp
#ifndef BOOST_PP_IS_ITERATING
///////////////////////////////////////////////////////////////////////////////
/// \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/proto/detail/prefix.hpp>
#include <boost/config.hpp>
#include <boost/utility/result_of.hpp>
#include <boost/preprocessor/cat.hpp>
#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/repetition/enum.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/proto/proto_fwd.hpp>
#include <boost/proto/args.hpp>
#include <boost/proto/detail/suffix.hpp>
namespace boost { namespace proto
{
namespace detail
{
template<typename Expr>
struct expr_params;
template<typename Tag, typename Args, long N>
struct expr_params<proto::expr<Tag, Args, N> >
{
typedef Tag tag;
typedef Args args;
BOOST_STATIC_CONSTANT(long, arity = N);
};
template<typename Expr, long Arity = expr_params<Expr>::arity>
struct by_value_generator_;
#define BOOST_PROTO_DEFINE_BY_VALUE_TYPE(Z, N, Expr) \
typename uncvref<typename expr_params<Expr>::args::BOOST_PP_CAT(child, N)>::type \
/**/
#define BOOST_PROTO_DEFINE_BY_VALUE(Z, N, expr) \
expr.BOOST_PP_CAT(child, N) \
/**/
template<typename Expr>
struct by_value_generator_<Expr, 0>
{
typedef
proto::expr<
typename expr_params<Expr>::tag
, term<typename detail::term_traits<typename expr_params<Expr>::args::child0>::value_type>
>
type;
static type const make(Expr const &expr)
{
type that = {expr.child0};
return that;
}
};
#define BOOST_PP_ITERATION_PARAMS_1 (3, (1, BOOST_PROTO_MAX_ARITY, <boost/proto/generate.hpp>))
#include BOOST_PP_ITERATE()
#undef BOOST_PROTO_DEFINE_BY_VALUE
#undef BOOST_PROTO_DEFINE_BY_VALUE_TYPE
}
BOOST_PROTO_BEGIN_ADL_NAMESPACE(generatorns_)
/// \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_HAS_DECLTYPE
Expr
#else
Expr const &
#endif
operator ()(Expr const &expr) const
{
return expr;
}
};
/// \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()
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 &expr) const
{
return Extends<Expr>(expr);
}
};
/// \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()
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 &expr) const
{
Extends<Expr> that = {expr};
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<void(Expr)>::type operator ()(Expr const &expr) const
{
return detail::by_value_generator_<Expr>::make(expr);
}
};
/// \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<
void(typename First::template result<void(Expr)>::type)
>::type
type;
};
template<typename This, typename Expr>
struct result<This(Expr &)>
{
typedef
typename Second::template result<
void(typename First::template result<void(Expr)>::type)
>::type
type;
};
template<typename This, typename Expr>
struct result<This(Expr const &)>
{
typedef
typename Second::template result<
void(typename First::template result<void(Expr)>::type)
>::type
type;
};
/// \param expr The expression to modify.
/// \return Second()(First()(expr))
template<typename Expr>
typename result<void(Expr)>::type operator ()(Expr const &expr) const
{
return Second()(First()(expr));
}
};
BOOST_PROTO_END_ADL_NAMESPACE(generatorns_)
/// 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_
{};
}}
#endif // BOOST_PROTO_GENERATE_HPP_EAN_02_13_2007
#else // BOOST_PP_IS_ITERATING
#define N BOOST_PP_ITERATION()
template<typename Expr>
struct by_value_generator_<Expr, N>
{
typedef
proto::expr<
typename expr_params<Expr>::tag
, BOOST_PP_CAT(list, N)<
// typename uncvref<typename expr_params<Expr>::args::child0>::type, ...
BOOST_PP_ENUM(N, BOOST_PROTO_DEFINE_BY_VALUE_TYPE, Expr)
>
>
type;
static type const make(Expr const &expr)
{
type that = {
// expr.child0, ...
BOOST_PP_ENUM(N, BOOST_PROTO_DEFINE_BY_VALUE, expr)
};
return that;
}
};
#undef N
#endif
