//----------------------------------------------------------------------------- | |
// boost variant/variant_fwd.hpp header file | |
// See http://www.boost.org for updates, documentation, and revision history. | |
//----------------------------------------------------------------------------- | |
// | |
// Copyright (c) 2003 | |
// Eric Friedman, Itay Maman | |
// | |
// 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_VARIANT_VARIANT_FWD_HPP | |
#define BOOST_VARIANT_VARIANT_FWD_HPP | |
#include "boost/variant/detail/config.hpp" | |
#include "boost/blank_fwd.hpp" | |
#include "boost/mpl/arg.hpp" | |
#include "boost/mpl/limits/arity.hpp" | |
#include "boost/mpl/aux_/na.hpp" | |
#include "boost/preprocessor/cat.hpp" | |
#include "boost/preprocessor/enum.hpp" | |
#include "boost/preprocessor/enum_params.hpp" | |
#include "boost/preprocessor/enum_shifted_params.hpp" | |
#include "boost/preprocessor/repeat.hpp" | |
/////////////////////////////////////////////////////////////////////////////// | |
// macro BOOST_VARIANT_LIMIT_TYPES | |
// | |
// Implementation-defined preprocessor symbol describing the actual | |
// length of variant's pseudo-variadic template parameter list. | |
// | |
#include "boost/mpl/limits/list.hpp" | |
#define BOOST_VARIANT_LIMIT_TYPES \ | |
BOOST_MPL_LIMIT_LIST_SIZE | |
/////////////////////////////////////////////////////////////////////////////// | |
// macro BOOST_VARIANT_NO_REFERENCE_SUPPORT | |
// | |
// Defined if variant does not support references as bounded types. | |
// | |
#if defined(BOOST_VARIANT_AUX_BROKEN_CONSTRUCTOR_TEMPLATE_ORDERING) \ | |
&& !defined(BOOST_VARIANT_AUX_HAS_CONSTRUCTOR_TEMPLATE_ORDERING_SFINAE_WKND) \ | |
&& !defined(BOOST_VARIANT_NO_REFERENCE_SUPPORT) | |
# define BOOST_VARIANT_NO_REFERENCE_SUPPORT | |
#endif | |
/////////////////////////////////////////////////////////////////////////////// | |
// macro BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT | |
// | |
// Defined if variant does not support make_variant_over (see below). | |
// | |
#if defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) | |
# define BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT | |
#endif | |
/////////////////////////////////////////////////////////////////////////////// | |
// macro BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT | |
// | |
// Defined if make_recursive_variant cannot be supported as documented. | |
// | |
// Note: Currently, MPL lambda facility is used as workaround if defined, and | |
// so only types declared w/ MPL lambda workarounds will work. | |
// | |
#include "boost/variant/detail/substitute_fwd.hpp" | |
#if defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) \ | |
&& !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT) | |
# define BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT | |
#endif | |
/////////////////////////////////////////////////////////////////////////////// | |
// macro BOOST_VARIANT_RECURSIVE_VARIANT_MAX_ARITY | |
// | |
// Exposes maximum allowed arity of class templates with recursive_variant | |
// arguments. That is, | |
// make_recursive_variant< ..., T<[1], recursive_variant_, ... [N]> >. | |
// | |
#include "boost/mpl/limits/arity.hpp" | |
#define BOOST_VARIANT_RECURSIVE_VARIANT_MAX_ARITY \ | |
BOOST_MPL_LIMIT_METAFUNCTION_ARITY | |
/////////////////////////////////////////////////////////////////////////////// | |
// macro BOOST_VARIANT_ENUM_PARAMS | |
// | |
// Convenience macro for enumeration of BOOST_VARIANT_LIMIT_TYPES params. | |
// | |
// Rationale: Cleaner, simpler code for clients of variant library. | |
// | |
#define BOOST_VARIANT_ENUM_PARAMS( param ) \ | |
BOOST_PP_ENUM_PARAMS(BOOST_VARIANT_LIMIT_TYPES, param) | |
/////////////////////////////////////////////////////////////////////////////// | |
// macro BOOST_VARIANT_ENUM_SHIFTED_PARAMS | |
// | |
// Convenience macro for enumeration of BOOST_VARIANT_LIMIT_TYPES-1 params. | |
// | |
#define BOOST_VARIANT_ENUM_SHIFTED_PARAMS( param ) \ | |
BOOST_PP_ENUM_SHIFTED_PARAMS(BOOST_VARIANT_LIMIT_TYPES, param) | |
namespace boost { | |
namespace detail { namespace variant { | |
/////////////////////////////////////////////////////////////////////////////// | |
// (detail) class void_ and class template convert_void | |
// | |
// Provides the mechanism by which void(NN) types are converted to | |
// mpl::void_ (and thus can be passed to mpl::list). | |
// | |
// Rationale: This is particularly needed for the using-declarations | |
// workaround (below), but also to avoid associating mpl namespace with | |
// variant in argument dependent lookups (which used to happen because of | |
// defaulting of template parameters to mpl::void_). | |
// | |
struct void_; | |
template <typename T> | |
struct convert_void | |
{ | |
typedef T type; | |
}; | |
template <> | |
struct convert_void< void_ > | |
{ | |
typedef mpl::na type; | |
}; | |
/////////////////////////////////////////////////////////////////////////////// | |
// (workaround) BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE | |
// | |
// Needed to work around compilers that don't support using-declaration | |
// overloads. (See the variant::initializer workarounds below.) | |
// | |
#if defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) | |
// (detail) tags voidNN -- NN defined on [0, BOOST_VARIANT_LIMIT_TYPES) | |
// | |
// Defines void types that are each unique and specializations of | |
// convert_void that yields mpl::na for each voidNN type. | |
// | |
#define BOOST_VARIANT_DETAIL_DEFINE_VOID_N(z,N,_) \ | |
struct BOOST_PP_CAT(void,N); \ | |
\ | |
template <> \ | |
struct convert_void< BOOST_PP_CAT(void,N) > \ | |
{ \ | |
typedef mpl::na type; \ | |
}; \ | |
/**/ | |
BOOST_PP_REPEAT( | |
BOOST_VARIANT_LIMIT_TYPES | |
, BOOST_VARIANT_DETAIL_DEFINE_VOID_N | |
, _ | |
) | |
#undef BOOST_VARIANT_DETAIL_DEFINE_VOID_N | |
#endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround | |
}} // namespace detail::variant | |
/////////////////////////////////////////////////////////////////////////////// | |
// (detail) macro BOOST_VARIANT_AUX_DECLARE_PARAM | |
// | |
// Template parameter list for variant and recursive_variant declarations. | |
// | |
#if !defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) | |
# define BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL(z, N, T) \ | |
typename BOOST_PP_CAT(T,N) = detail::variant::void_ \ | |
/**/ | |
#else // defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) | |
# define BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL(z, N, T) \ | |
typename BOOST_PP_CAT(T,N) = BOOST_PP_CAT(detail::variant::void,N) \ | |
/**/ | |
#endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround | |
#define BOOST_VARIANT_AUX_DECLARE_PARAMS \ | |
BOOST_PP_ENUM( \ | |
BOOST_VARIANT_LIMIT_TYPES \ | |
, BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL \ | |
, T \ | |
) \ | |
/**/ | |
/////////////////////////////////////////////////////////////////////////////// | |
// class template variant (concept inspired by Andrei Alexandrescu) | |
// | |
// Efficient, type-safe bounded discriminated union. | |
// | |
// Preconditions: | |
// - Each type must be unique. | |
// - No type may be const-qualified. | |
// | |
// Proper declaration form: | |
// variant<types> (where types is a type-sequence) | |
// or | |
// variant<T0,T1,...,Tn> (where T0 is NOT a type-sequence) | |
// | |
template < BOOST_VARIANT_AUX_DECLARE_PARAMS > class variant; | |
/////////////////////////////////////////////////////////////////////////////// | |
// metafunction make_recursive_variant | |
// | |
// Exposes a boost::variant with recursive_variant_ tags (below) substituted | |
// with the variant itself (wrapped as needed with boost::recursive_wrapper). | |
// | |
template < BOOST_VARIANT_AUX_DECLARE_PARAMS > struct make_recursive_variant; | |
#undef BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL | |
#undef BOOST_VARIANT_AUX_DECLARE_PARAMS | |
/////////////////////////////////////////////////////////////////////////////// | |
// type recursive_variant_ | |
// | |
// Tag type indicates where recursive variant substitution should occur. | |
// | |
#if !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT) | |
struct recursive_variant_; | |
#else | |
typedef mpl::arg<1> recursive_variant_; | |
#endif | |
/////////////////////////////////////////////////////////////////////////////// | |
// metafunction make_variant_over | |
// | |
// Result is a variant w/ types of the specified type sequence. | |
// | |
template <typename Types> struct make_variant_over; | |
/////////////////////////////////////////////////////////////////////////////// | |
// metafunction make_recursive_variant_over | |
// | |
// Result is a recursive variant w/ types of the specified type sequence. | |
// | |
template <typename Types> struct make_recursive_variant_over; | |
} // namespace boost | |
#endif // BOOST_VARIANT_VARIANT_FWD_HPP |