boost/proto/transform/make.hpp
#ifndef BOOST_PP_IS_ITERATING
///////////////////////////////////////////////////////////////////////////////
/// \file make.hpp
/// Contains definition of the make<> transform.
//
// 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_MAKE_HPP_EAN_12_02_2007
#define BOOST_PROTO_TRANSFORM_MAKE_HPP_EAN_12_02_2007
#include <boost/proto/detail/prefix.hpp>
#include <boost/detail/workaround.hpp>
#include <boost/preprocessor/repetition/enum.hpp>
#include <boost/preprocessor/repetition/enum_params.hpp>
#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
#include <boost/preprocessor/repetition/enum_binary_params.hpp>
#include <boost/preprocessor/repetition/enum_params_with_a_default.hpp>
#include <boost/preprocessor/repetition/repeat_from_to.hpp>
#include <boost/preprocessor/facilities/intercept.hpp>
#include <boost/preprocessor/cat.hpp>
#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/selection/max.hpp>
#include <boost/preprocessor/arithmetic/inc.hpp>
#include <boost/mpl/aux_/has_type.hpp>
#include <boost/mpl/aux_/template_arity.hpp>
#include <boost/mpl/aux_/lambda_arity_param.hpp>
#include <boost/utility/result_of.hpp>
#include <boost/type_traits/remove_const.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/proto/proto_fwd.hpp>
#include <boost/proto/traits.hpp>
#include <boost/proto/args.hpp>
#include <boost/proto/transform/impl.hpp>
#include <boost/proto/detail/as_lvalue.hpp>
#include <boost/proto/detail/ignore_unused.hpp>
#include <boost/proto/detail/suffix.hpp>
namespace boost { namespace proto
{
namespace detail
{
template<BOOST_PP_ENUM_PARAMS_WITH_A_DEFAULT(BOOST_PROTO_MAX_ARITY, typename A, void)>
struct typelist
{
typedef void type;
};
template<typename T, bool HasType = mpl::aux::has_type<T>::value>
struct nested_type
{
typedef typename T::type type;
};
template<typename T>
struct nested_type<T, false>
{
typedef T type;
};
template<typename T, typename Args, typename Void = void>
struct nested_type_if
: nested_type<T>
{};
template<typename R, typename Expr, typename State, typename Data
// BUGBUG this should be is_transform, but if R is a template instantiation
// it will cause the template to be instantiated, whereas is_callable will not.
, bool IsTransform = is_callable<R>::value
>
struct make_if_;
template<typename R, typename Expr, typename State, typename Data
BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(long Arity = mpl::aux::template_arity<R>::value)
>
struct make_
{
typedef R type;
typedef void not_applied_;
};
template<typename R, typename Expr, typename State, typename Data>
struct make_if_<R, Expr, State, Data, false>
: make_<R, Expr, State, Data>
{};
#if BOOST_WORKAROUND(__GNUC__, == 3) || (__GNUC__ == 4 && __GNUC_MINOR__ == 0)
// work around GCC bug
template<typename Tag, typename Args, long N, typename Expr, typename State, typename Data>
struct make_if_<proto::expr<Tag, Args, N>, Expr, State, Data, false>
{
typedef proto::expr<Tag, Args, N> type;
typedef void not_applied_;
};
#endif
// TODO could optimize this if R is a transform
template<typename R, typename Expr, typename State, typename Data>
struct make_if_<R, Expr, State, Data, true>
: remove_const<
typename remove_reference<
typename R::template impl<Expr, State, Data>::result_type
>::type
>
{};
template<typename Type, bool IsAggregate = is_aggregate<Type>::value>
struct construct_
{
typedef Type result_type;
Type operator ()() const
{
return Type();
}
#define TMP(Z, N, DATA) \
template<BOOST_PP_ENUM_PARAMS_Z(Z, N, typename A)> \
Type operator ()(BOOST_PP_ENUM_BINARY_PARAMS_Z(Z, N, A, &a)) const \
{ \
return Type(BOOST_PP_ENUM_PARAMS_Z(Z, N, a)); \
}
BOOST_PP_REPEAT_FROM_TO(1, BOOST_PP_INC(BOOST_PROTO_MAX_ARITY), TMP, ~)
#undef TMP
};
template<typename Type>
struct construct_<Type, true>
{
typedef Type result_type;
Type operator ()() const
{
return Type();
}
#define TMP(Z, N, DATA) \
template<BOOST_PP_ENUM_PARAMS_Z(Z, N, typename A)> \
Type operator ()(BOOST_PP_ENUM_BINARY_PARAMS_Z(Z, N, A, &a)) const \
{ \
Type that = {BOOST_PP_ENUM_PARAMS_Z(Z, N, a)}; \
return that; \
}
BOOST_PP_REPEAT_FROM_TO(1, BOOST_PP_INC(BOOST_PROTO_MAX_ARITY), TMP, ~)
#undef TMP
};
#define TMP(Z, N, DATA) \
template<typename Type BOOST_PP_ENUM_TRAILING_PARAMS_Z(Z, N, typename A)> \
Type construct(BOOST_PP_ENUM_BINARY_PARAMS_Z(Z, N, A, &a)) \
{ \
return construct_<Type>()(BOOST_PP_ENUM_PARAMS_Z(Z, N, a)); \
}
BOOST_PP_REPEAT(BOOST_PROTO_MAX_ARITY, TMP, ~)
#undef TMP
}
/// \brief A PrimitiveTransform which prevents another PrimitiveTransform
/// from being applied in an \c ObjectTransform.
///
/// When building higher order transforms with <tt>make\<\></tt> or
/// <tt>lazy\<\></tt>, you sometimes would like to build types that
/// are parameterized with Proto transforms. In such lambda-style
/// transforms, Proto will unhelpfully find all nested transforms
/// and apply them, even if you don't want them to be applied. Consider
/// the following transform, which will replace the \c _ in
/// <tt>Bar<_>()</tt> with <tt>proto::terminal\<int\>::type</tt>:
///
/// \code
/// template<typename T>
/// struct Bar
/// {};
///
/// struct Foo
/// : proto::when<_, Bar<_>() >
/// {};
///
/// proto::terminal<int>::type i = {0};
///
/// int main()
/// {
/// Foo()(i);
/// std::cout << typeid(Foo()(i)).name() << std::endl;
/// }
/// \endcode
///
/// If you actually wanted to default-construct an object of type
/// <tt>Bar\<_\></tt>, you would have to protect the \c _ to prevent
/// it from being applied. You can use <tt>proto::protect\<\></tt>
/// as follows:
///
/// \code
/// // OK: replace anything with Bar<_>()
/// struct Foo
/// : proto::when<_, Bar<protect<_> >() >
/// {};
/// \endcode
template<typename PrimitiveTransform>
struct protect : transform<protect<PrimitiveTransform> >
{
template<typename, typename, typename>
struct impl
{
typedef PrimitiveTransform result_type;
};
};
/// \brief A PrimitiveTransform which computes a type by evaluating any
/// nested transforms and then constructs an object of that type.
///
/// The <tt>make\<\></tt> transform checks to see if \c Object is a template.
/// If it is, the template type is disassembled to find nested transforms.
/// Proto considers the following types to represent transforms:
///
/// \li Function types
/// \li Function pointer types
/// \li Types for which <tt>proto::is_callable\< type \>::::value</tt> is \c true
///
/// <tt>boost::result_of\<make\<T\<X0,X1,...\> \>(Expr, State, Data)\>::::type</tt>
/// is evaluated as follows. For each \c X in <tt>X0,X1,...</tt>, do:
///
/// \li If \c X is a template like <tt>U\<Y0,Y1,...\></tt>, then let <tt>X'</tt>
/// be <tt>boost::result_of\<make\<U\<Y0,Y1,...\> \>(Expr, State, Data)\>::::type</tt>
/// (which evaluates this procedure recursively). Note whether any
/// substitutions took place during this operation.
/// \li Otherwise, if \c X is a transform, then let <tt>X'</tt> be
/// <tt>boost::result_of\<when\<_, X\>(Expr, State, Data)\>::::type</tt>.
/// Note that a substitution took place.
/// \li Otherwise, let <tt>X'</tt> be \c X, and note that no substitution
/// took place.
/// \li If any substitutions took place in any of the above steps and
/// <tt>T\<X0',X1',...\></tt> has a nested <tt>::type</tt> typedef,
/// the result type is <tt>T\<X0',X1',...\>::::type</tt>.
/// \li Otherwise, the result type is <tt>T\<X0',X1',...\></tt>.
///
/// Note that <tt>when\<\></tt> is implemented in terms of <tt>call\<\></tt>
/// and <tt>make\<\></tt>, so the above procedure is evaluated recursively.
template<typename Object>
struct make : transform<make<Object> >
{
template<typename Expr, typename State, typename Data>
struct impl : transform_impl<Expr, State, Data>
{
typedef typename detail::make_if_<Object, Expr, State, Data>::type result_type;
/// \return <tt>result_type()</tt>
result_type operator ()(
typename impl::expr_param
, typename impl::state_param
, typename impl::data_param
) const
{
return result_type();
}
};
};
#define BOOST_PP_ITERATION_PARAMS_1 (3, (0, BOOST_PROTO_MAX_ARITY, <boost/proto/transform/make.hpp>))
#include BOOST_PP_ITERATE()
/// INTERNAL ONLY
///
template<typename Object>
struct is_callable<make<Object> >
: mpl::true_
{};
/// INTERNAL ONLY
///
template<typename PrimitiveTransform>
struct is_callable<protect<PrimitiveTransform> >
: mpl::true_
{};
}}
#endif
#else
#define N BOOST_PP_ITERATION()
namespace detail
{
#if N > 0
template<typename T BOOST_PP_ENUM_TRAILING_PARAMS(N, typename A)>
struct nested_type_if<
T
, typelist<BOOST_PP_ENUM_PARAMS(N, A)>
, typename typelist<
BOOST_PP_ENUM_BINARY_PARAMS(N, typename A, ::not_applied_ BOOST_PP_INTERCEPT)
>::type
>
{
typedef T type;
typedef void not_applied_;
};
#define TMP0(Z, M, DATA) make_if_<BOOST_PP_CAT(A, M), Expr, State, Data>
#define TMP1(Z, M, DATA) typename TMP0(Z, M, DATA) ::type
template<
template<BOOST_PP_ENUM_PARAMS(N, typename BOOST_PP_INTERCEPT)> class R
BOOST_PP_ENUM_TRAILING_PARAMS(N, typename A)
, typename Expr, typename State, typename Data
>
struct make_<R<BOOST_PP_ENUM_PARAMS(N, A)>, Expr, State, Data
BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(N)
>
: nested_type_if<
R<BOOST_PP_ENUM(N, TMP1, ~)>
, typelist<BOOST_PP_ENUM(N, TMP0, ~) >
>
{};
template<
template<BOOST_PP_ENUM_PARAMS(N, typename BOOST_PP_INTERCEPT)> class R
BOOST_PP_ENUM_TRAILING_PARAMS(N, typename A)
, typename Expr, typename State, typename Data
>
struct make_<noinvoke<R<BOOST_PP_ENUM_PARAMS(N, A)> >, Expr, State, Data
BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(N)
>
{
typedef R<BOOST_PP_ENUM(N, TMP1, ~)> type;
};
#undef TMP0
#undef TMP1
#endif
template<
typename R
BOOST_PP_ENUM_TRAILING_PARAMS(N, typename A)
, typename Expr, typename State, typename Data
>
struct make_if_<R(BOOST_PP_ENUM_PARAMS(N, A)), Expr, State, Data, false>
{
typedef
typename remove_const<
typename remove_reference<
typename when<_, R(BOOST_PP_ENUM_PARAMS(N, A))>
::template impl<Expr, State, Data>::result_type
>::type
>::type
type;
};
template<
typename R
BOOST_PP_ENUM_TRAILING_PARAMS(N, typename A)
, typename Expr, typename State, typename Data
>
struct make_if_<R(*)(BOOST_PP_ENUM_PARAMS(N, A)), Expr, State, Data, false>
{
typedef
typename remove_const<
typename remove_reference<
typename when<_, R(BOOST_PP_ENUM_PARAMS(N, A))>
::template impl<Expr, State, Data>::result_type
>::type
>::type
type;
};
template<typename T, typename A>
struct construct_<proto::expr<T, A, N>, true>
{
typedef proto::expr<T, A, N> result_type;
template<BOOST_PP_ENUM_PARAMS(BOOST_PP_MAX(N, 1), typename A)>
result_type operator ()(BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_MAX(N, 1), A, &a)) const
{
return result_type::make(BOOST_PP_ENUM_PARAMS(BOOST_PP_MAX(N, 1), a));
}
};
}
/// \brief A PrimitiveTransform which computes a type by evaluating any
/// nested transforms and then constructs an object of that type with the
/// current expression, state and data, transformed according
/// to \c A0 through \c AN.
template<typename Object BOOST_PP_ENUM_TRAILING_PARAMS(N, typename A)>
struct make<Object(BOOST_PP_ENUM_PARAMS(N, A))>
: transform<make<Object(BOOST_PP_ENUM_PARAMS(N, A))> >
{
template<typename Expr, typename State, typename Data>
struct impl : transform_impl<Expr, State, Data>
{
/// \brief <tt>boost::result_of\<make\<Object\>(Expr, State, Data)\>::::type</tt>
typedef typename detail::make_if_<Object, Expr, State, Data>::type result_type;
//typedef typename detail::make_<Object, Expr, State, Data>::type result_type;
/// Let \c ax be <tt>when\<_, Ax\>()(e, s, d)</tt>
/// for each \c x in <tt>[0,N]</tt>.
/// Return <tt>result_type(a0, a1,... aN)</tt>.
///
/// \param e The current expression
/// \param s The current state
/// \param d An arbitrary data
result_type operator ()(
typename impl::expr_param e
, typename impl::state_param s
, typename impl::data_param d
) const
{
proto::detail::ignore_unused(e);
proto::detail::ignore_unused(s);
proto::detail::ignore_unused(d);
return detail::construct<result_type>(
#define TMP(Z, M, DATA) \
detail::as_lvalue( \
typename when<_, BOOST_PP_CAT(A, M)> \
::template impl<Expr, State, Data>()(e, s, d) \
)
BOOST_PP_ENUM(N, TMP, DATA)
#undef TMP
);
}
};
};
#if BOOST_WORKAROUND(__GNUC__, == 3) || (__GNUC__ == 4 && __GNUC_MINOR__ == 0)
// work around GCC bug
template<typename Tag, typename Args, long Arity BOOST_PP_ENUM_TRAILING_PARAMS(N, typename A)>
struct make<proto::expr<Tag, Args, Arity>(BOOST_PP_ENUM_PARAMS(N, A))>
: transform<make<proto::expr<Tag, Args, Arity>(BOOST_PP_ENUM_PARAMS(N, A))> >
{
template<typename Expr, typename State, typename Data>
struct impl : transform_impl<Expr, State, Data>
{
typedef proto::expr<Tag, Args, Arity> result_type;
result_type operator ()(
typename impl::expr_param e
, typename impl::state_param s
, typename impl::data_param d
) const
{
return proto::expr<Tag, Args, Arity>::make(
#define TMP(Z, M, DATA) \
detail::as_lvalue( \
typename when<_, BOOST_PP_CAT(A, M)> \
::template impl<Expr, State, Data>()(e, s, d) \
)
BOOST_PP_ENUM(N, TMP, DATA)
#undef TMP
);
}
};
};
#endif
#undef N
#endif
