boost/xpressive/proto/transform/fold.hpp
#ifndef BOOST_PP_IS_ITERATING
///////////////////////////////////////////////////////////////////////////////
/// \file fold.hpp
/// Contains definition of the fold<> and reverse_fold<> transforms.
//
// 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_TRANSFORM_FOLD_HPP_EAN_11_04_2007
#define BOOST_PROTO_TRANSFORM_FOLD_HPP_EAN_11_04_2007
#include <boost/xpressive/proto/detail/prefix.hpp>
#include <boost/version.hpp>
#include <boost/preprocessor/cat.hpp>
#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/arithmetic/inc.hpp>
#include <boost/preprocessor/arithmetic/sub.hpp>
#include <boost/preprocessor/repetition/repeat.hpp>
#if BOOST_VERSION >= 103500
#include <boost/fusion/include/fold.hpp>
#else
#include <boost/spirit/fusion/algorithm/fold.hpp>
#endif
#include <boost/xpressive/proto/proto_fwd.hpp>
#include <boost/xpressive/proto/fusion.hpp>
#include <boost/xpressive/proto/traits.hpp>
#include <boost/xpressive/proto/transform/call.hpp>
#include <boost/xpressive/proto/detail/suffix.hpp>
namespace boost { namespace proto
{
namespace transform
{
namespace detail
{
template<typename Transform, typename Visitor>
struct as_callable
{
as_callable(Visitor &v)
: v_(v)
{}
template<typename Sig>
struct result;
template<typename This, typename Expr, typename State>
struct result<This(Expr, State)>
{
typedef
typename when<_, Transform>::template result<void(
BOOST_PROTO_UNCVREF(Expr)
, BOOST_PROTO_UNCVREF(State)
, Visitor
)>::type
type;
};
#if BOOST_VERSION < 103500
template<typename Expr, typename State>
struct apply : result<void(Expr, State)> {};
#endif
template<typename Expr, typename State>
typename when<_, Transform>::template result<void(Expr, State, Visitor)>::type
operator ()(Expr const &expr, State const &state) const
{
return when<_, Transform>()(expr, state, this->v_);
}
private:
Visitor &v_;
};
#if BOOST_VERSION < 103500
template<typename Sequence, typename Void = void>
struct as_fusion_sequence_type
{
typedef Sequence const type;
};
template<typename Sequence>
Sequence const &as_fusion_sequence(Sequence const &sequence, ...)
{
return sequence;
}
template<typename Sequence>
struct as_fusion_sequence_type<Sequence, typename Sequence::proto_is_expr_>
{
typedef typename Sequence::proto_base_expr const type;
};
template<typename Sequence>
typename Sequence::proto_base_expr const &as_fusion_sequence(Sequence const &sequence, int)
{
return sequence.proto_base();
}
#define BOOST_PROTO_AS_FUSION_SEQUENCE_TYPE(X) typename detail::as_fusion_sequence_type<X>::type
#define BOOST_PROTO_AS_FUSION_SEQUENCE(X) detail::as_fusion_sequence(X, 0)
#else
#define BOOST_PROTO_AS_FUSION_SEQUENCE_TYPE(X) X
#define BOOST_PROTO_AS_FUSION_SEQUENCE(X) X
#endif
template<typename Fun, typename Expr, typename State, typename Visitor, long Arity = Expr::proto_arity::value>
struct fold_impl
{};
template<typename Fun, typename Expr, typename State, typename Visitor, long Arity = Expr::proto_arity::value>
struct reverse_fold_impl
{};
#define BOOST_PROTO_ARG_N_TYPE(n)\
BOOST_PP_CAT(proto_arg, n)\
/**/
#define BOOST_PROTO_FOLD_STATE_TYPE(z, n, data)\
typedef\
typename when<_, Fun>::template result<void(\
typename Expr::BOOST_PROTO_ARG_N_TYPE(n)::proto_base_expr\
, BOOST_PP_CAT(state, n)\
, Visitor\
)>::type\
BOOST_PP_CAT(state, BOOST_PP_INC(n));\
/**/
#define BOOST_PROTO_FOLD_STATE(z, n, data)\
BOOST_PP_CAT(state, BOOST_PP_INC(n)) const &BOOST_PP_CAT(s, BOOST_PP_INC(n)) =\
when<_, Fun>()(expr.BOOST_PP_CAT(arg, n).proto_base(), BOOST_PP_CAT(s, n), visitor);\
/**/
#define BOOST_PROTO_REVERSE_FOLD_STATE_TYPE(z, n, data)\
typedef\
typename when<_, Fun>::template result<void(\
typename Expr::BOOST_PROTO_ARG_N_TYPE(BOOST_PP_SUB(data, BOOST_PP_INC(n)))::proto_base_expr\
, BOOST_PP_CAT(state, BOOST_PP_SUB(data, n))\
, Visitor\
)>::type\
BOOST_PP_CAT(state, BOOST_PP_SUB(data, BOOST_PP_INC(n)));\
/**/
#define BOOST_PROTO_REVERSE_FOLD_STATE(z, n, data)\
BOOST_PP_CAT(state, BOOST_PP_SUB(data, BOOST_PP_INC(n))) const &BOOST_PP_CAT(s, BOOST_PP_SUB(data, BOOST_PP_INC(n))) =\
when<_, Fun>()(expr.BOOST_PP_CAT(arg, BOOST_PP_SUB(data, BOOST_PP_INC(n))).proto_base(), BOOST_PP_CAT(s, BOOST_PP_SUB(data, n)), visitor);\
/**/
#define BOOST_PP_ITERATION_PARAMS_1 (3, (1, BOOST_PROTO_MAX_ARITY, <boost/xpressive/proto/transform/fold.hpp>))
#include BOOST_PP_ITERATE()
#undef BOOST_PROTO_REVERSE_FOLD_STATE
#undef BOOST_PROTO_REVERSE_FOLD_STATE_TYPE
#undef BOOST_PROTO_FOLD_STATE
#undef BOOST_PROTO_FOLD_STATE_TYPE
#undef BOOST_PROTO_ARG_N_TYPE
} // namespace detail
/// \brief A PrimitiveTransform that invokes the <tt>fusion::fold\<\></tt>
/// algorithm to accumulate
template<typename Sequence, typename State0, typename Fun>
struct fold : proto::callable
{
template<typename Sig>
struct result;
template<typename This, typename Expr, typename State, typename Visitor>
struct result<This(Expr, State, Visitor)>
{
/// \brief A Fusion sequence.
typedef
typename when<_, Sequence>::template result<void(Expr, State, Visitor)>::type
sequence;
/// \brief An initial state for the fold.
typedef
typename when<_, State0>::template result<void(Expr, State, Visitor)>::type
state0;
/// \brief <tt>fun(v)(e,s) == when\<_,Fun\>()(e,s,v)</tt>
typedef
detail::as_callable<Fun, Visitor>
fun;
typedef
typename fusion::BOOST_PROTO_FUSION_RESULT_OF::fold<
BOOST_PROTO_AS_FUSION_SEQUENCE_TYPE(sequence)
, state0
, fun
>::type
type;
};
/// Let \c seq be <tt>when\<_, Sequence\>()(expr, state, visitor)</tt>, let
/// \c state0 be <tt>when\<_, State0\>()(expr, state, visitor)</tt>, and
/// let \c fun(visitor) be an object such that <tt>fun(visitor)(expr, state)</tt>
/// is equivalent to <tt>when\<_, Fun\>()(expr, state, visitor)</tt>. Then, this
/// function returns <tt>fusion::fold(seq, state0, fun(visitor))</tt>.
///
/// \param expr The current expression
/// \param state The current state
/// \param visitor An arbitrary visitor
template<typename Expr, typename State, typename Visitor>
typename result<void(Expr, State, Visitor)>::type
operator ()(Expr const &expr, State const &state, Visitor &visitor) const
{
when<_, Sequence> sequence;
detail::as_callable<Fun, Visitor> fun(visitor);
return fusion::fold(
BOOST_PROTO_AS_FUSION_SEQUENCE(sequence(expr, state, visitor))
, when<_, State0>()(expr, state, visitor)
, fun
);
}
};
/// \brief A PrimitiveTransform that is the same as the
/// <tt>fold\<\></tt> transform, except that it folds
/// back-to-front instead of front-to-back. It uses
/// the \c _reverse callable PolymorphicFunctionObject
/// to create a <tt>fusion::reverse_view\<\></tt> of the
/// sequence before invoking <tt>fusion::fold\<\></tt>.
template<typename Sequence, typename State0, typename Fun>
struct reverse_fold
: fold<call<_reverse(Sequence)>, State0, Fun>
{};
// This specialization is only for improved compile-time performance
// in the commom case when the Sequence transform is \c proto::_.
//
/// INTERNAL ONLY
///
template<typename State0, typename Fun>
struct fold<_, State0, Fun> : proto::callable
{
template<typename Sig>
struct result;
template<typename This, typename Expr, typename State, typename Visitor>
struct result<This(Expr, State, Visitor)>
{
typedef
typename detail::fold_impl<
Fun
, typename Expr::proto_base_expr
, typename when<_, State0>::template result<void(Expr, State, Visitor)>::type
, Visitor
>::type
type;
};
template<typename Expr, typename State, typename Visitor>
typename result<void(Expr, State, Visitor)>::type
operator ()(Expr const &expr, State const &state, Visitor &visitor) const
{
typedef
detail::fold_impl<
Fun
, typename Expr::proto_base_expr
, typename when<_, State0>::template result<void(Expr, State, Visitor)>::type
, Visitor
>
impl;
return impl::call(
expr.proto_base()
, when<_, State0>()(expr, state, visitor)
, visitor
);
}
};
// This specialization is only for improved compile-time performance
// in the commom case when the Sequence transform is \c proto::_.
//
/// INTERNAL ONLY
///
template<typename State0, typename Fun>
struct reverse_fold<_, State0, Fun> : proto::callable
{
template<typename Sig>
struct result;
template<typename This, typename Expr, typename State, typename Visitor>
struct result<This(Expr, State, Visitor)>
{
typedef
typename detail::reverse_fold_impl<
Fun
, typename Expr::proto_base_expr
, typename when<_, State0>::template result<void(Expr, State, Visitor)>::type
, Visitor
>::type
type;
};
template<typename Expr, typename State, typename Visitor>
typename result<void(Expr, State, Visitor)>::type
operator ()(Expr const &expr, State const &state, Visitor &visitor) const
{
typedef
detail::reverse_fold_impl<
Fun
, typename Expr::proto_base_expr
, typename when<_, State0>::template result<void(Expr, State, Visitor)>::type
, Visitor
>
impl;
return impl::call(
expr.proto_base()
, when<_, State0>()(expr, state, visitor)
, visitor
);
}
};
}
/// INTERNAL ONLY
///
template<typename Sequence, typename State, typename Fun>
struct is_callable<transform::fold<Sequence, State, Fun> >
: mpl::true_
{};
/// INTERNAL ONLY
///
template<typename Sequence, typename State, typename Fun>
struct is_callable<transform::reverse_fold<Sequence, State, Fun> >
: mpl::true_
{};
}}
#endif
#else
#define N BOOST_PP_ITERATION()
template<typename Fun, typename Expr, typename state0, typename Visitor>
struct fold_impl<Fun, Expr, state0, Visitor, N>
{
BOOST_PP_REPEAT(N, BOOST_PROTO_FOLD_STATE_TYPE, N)
typedef BOOST_PP_CAT(state, N) type;
static type call(Expr const &expr, state0 const &s0, Visitor &visitor)
{
BOOST_PP_REPEAT(N, BOOST_PROTO_FOLD_STATE, N)
return BOOST_PP_CAT(s, N);
}
};
template<typename Fun, typename Expr, typename BOOST_PP_CAT(state, N), typename Visitor>
struct reverse_fold_impl<Fun, Expr, BOOST_PP_CAT(state, N), Visitor, N>
{
BOOST_PP_REPEAT(N, BOOST_PROTO_REVERSE_FOLD_STATE_TYPE, N)
typedef state0 type;
static type call(Expr const &expr, BOOST_PP_CAT(state, N) const &BOOST_PP_CAT(s, N), Visitor &visitor)
{
BOOST_PP_REPEAT(N, BOOST_PROTO_REVERSE_FOLD_STATE, N)
return s0;
}
};
#undef N
#endif
