| //----------------------------------------------------------------------------- |
| // 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 |