//-----------------------------------------------------------------------------

// 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