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253 lines
8.5 KiB
253 lines
8.5 KiB
//----------------------------------------------------------------------------- |
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// boost variant/variant_fwd.hpp header file |
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// See http://www.boost.org for updates, documentation, and revision history. |
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//----------------------------------------------------------------------------- |
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// |
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// Copyright (c) 2003 |
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// Eric Friedman, Itay Maman |
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// |
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// Distributed under the Boost Software License, Version 1.0. (See |
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// accompanying file LICENSE_1_0.txt or copy at |
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// http://www.boost.org/LICENSE_1_0.txt) |
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#ifndef BOOST_VARIANT_VARIANT_FWD_HPP |
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#define BOOST_VARIANT_VARIANT_FWD_HPP |
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#include "boost/variant/detail/config.hpp" |
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#include "boost/blank_fwd.hpp" |
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#include "boost/mpl/arg.hpp" |
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#include "boost/mpl/limits/arity.hpp" |
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#include "boost/mpl/aux_/na.hpp" |
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#include "boost/preprocessor/cat.hpp" |
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#include "boost/preprocessor/enum.hpp" |
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#include "boost/preprocessor/enum_params.hpp" |
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#include "boost/preprocessor/enum_shifted_params.hpp" |
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#include "boost/preprocessor/repeat.hpp" |
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/////////////////////////////////////////////////////////////////////////////// |
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// macro BOOST_VARIANT_LIMIT_TYPES |
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// |
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// Implementation-defined preprocessor symbol describing the actual |
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// length of variant's pseudo-variadic template parameter list. |
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// |
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#include "boost/mpl/limits/list.hpp" |
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#define BOOST_VARIANT_LIMIT_TYPES \ |
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BOOST_MPL_LIMIT_LIST_SIZE |
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/////////////////////////////////////////////////////////////////////////////// |
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// macro BOOST_VARIANT_NO_REFERENCE_SUPPORT |
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// |
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// Defined if variant does not support references as bounded types. |
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// |
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#if defined(BOOST_VARIANT_AUX_BROKEN_CONSTRUCTOR_TEMPLATE_ORDERING) \ |
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&& !defined(BOOST_VARIANT_AUX_HAS_CONSTRUCTOR_TEMPLATE_ORDERING_SFINAE_WKND) \ |
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&& !defined(BOOST_VARIANT_NO_REFERENCE_SUPPORT) |
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# define BOOST_VARIANT_NO_REFERENCE_SUPPORT |
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#endif |
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/////////////////////////////////////////////////////////////////////////////// |
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// macro BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT |
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// |
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// Defined if variant does not support make_variant_over (see below). |
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// |
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#if defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) |
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# define BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT |
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#endif |
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/////////////////////////////////////////////////////////////////////////////// |
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// macro BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT |
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// |
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// Defined if make_recursive_variant cannot be supported as documented. |
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// |
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// Note: Currently, MPL lambda facility is used as workaround if defined, and |
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// so only types declared w/ MPL lambda workarounds will work. |
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// |
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#include "boost/variant/detail/substitute_fwd.hpp" |
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#if defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) \ |
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&& !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT) |
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# define BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT |
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#endif |
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/////////////////////////////////////////////////////////////////////////////// |
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// macro BOOST_VARIANT_RECURSIVE_VARIANT_MAX_ARITY |
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// |
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// Exposes maximum allowed arity of class templates with recursive_variant |
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// arguments. That is, |
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// make_recursive_variant< ..., T<[1], recursive_variant_, ... [N]> >. |
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// |
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#include "boost/mpl/limits/arity.hpp" |
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#define BOOST_VARIANT_RECURSIVE_VARIANT_MAX_ARITY \ |
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BOOST_MPL_LIMIT_METAFUNCTION_ARITY |
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/////////////////////////////////////////////////////////////////////////////// |
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// macro BOOST_VARIANT_ENUM_PARAMS |
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// |
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// Convenience macro for enumeration of BOOST_VARIANT_LIMIT_TYPES params. |
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// |
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// Rationale: Cleaner, simpler code for clients of variant library. |
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// |
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#define BOOST_VARIANT_ENUM_PARAMS( param ) \ |
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BOOST_PP_ENUM_PARAMS(BOOST_VARIANT_LIMIT_TYPES, param) |
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/////////////////////////////////////////////////////////////////////////////// |
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// macro BOOST_VARIANT_ENUM_SHIFTED_PARAMS |
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// |
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// Convenience macro for enumeration of BOOST_VARIANT_LIMIT_TYPES-1 params. |
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// |
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#define BOOST_VARIANT_ENUM_SHIFTED_PARAMS( param ) \ |
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BOOST_PP_ENUM_SHIFTED_PARAMS(BOOST_VARIANT_LIMIT_TYPES, param) |
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namespace boost { |
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namespace detail { namespace variant { |
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/////////////////////////////////////////////////////////////////////////////// |
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// (detail) class void_ and class template convert_void |
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// |
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// Provides the mechanism by which void(NN) types are converted to |
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// mpl::void_ (and thus can be passed to mpl::list). |
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// |
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// Rationale: This is particularly needed for the using-declarations |
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// workaround (below), but also to avoid associating mpl namespace with |
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// variant in argument dependent lookups (which used to happen because of |
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// defaulting of template parameters to mpl::void_). |
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// |
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struct void_; |
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template <typename T> |
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struct convert_void |
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{ |
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typedef T type; |
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}; |
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template <> |
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struct convert_void< void_ > |
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{ |
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typedef mpl::na type; |
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}; |
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/////////////////////////////////////////////////////////////////////////////// |
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// (workaround) BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE |
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// |
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// Needed to work around compilers that don't support using-declaration |
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// overloads. (See the variant::initializer workarounds below.) |
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// |
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#if defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) |
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// (detail) tags voidNN -- NN defined on [0, BOOST_VARIANT_LIMIT_TYPES) |
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// |
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// Defines void types that are each unique and specializations of |
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// convert_void that yields mpl::na for each voidNN type. |
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// |
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#define BOOST_VARIANT_DETAIL_DEFINE_VOID_N(z,N,_) \ |
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struct BOOST_PP_CAT(void,N); \ |
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\ |
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template <> \ |
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struct convert_void< BOOST_PP_CAT(void,N) > \ |
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{ \ |
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typedef mpl::na type; \ |
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}; \ |
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/**/ |
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BOOST_PP_REPEAT( |
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BOOST_VARIANT_LIMIT_TYPES |
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, BOOST_VARIANT_DETAIL_DEFINE_VOID_N |
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, _ |
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) |
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#undef BOOST_VARIANT_DETAIL_DEFINE_VOID_N |
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#endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround |
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}} // namespace detail::variant |
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/////////////////////////////////////////////////////////////////////////////// |
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// (detail) macro BOOST_VARIANT_AUX_DECLARE_PARAM |
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// |
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// Template parameter list for variant and recursive_variant declarations. |
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// |
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#if !defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) |
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# define BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL(z, N, T) \ |
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typename BOOST_PP_CAT(T,N) = detail::variant::void_ \ |
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/**/ |
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#else // defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) |
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# define BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL(z, N, T) \ |
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typename BOOST_PP_CAT(T,N) = BOOST_PP_CAT(detail::variant::void,N) \ |
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/**/ |
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#endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround |
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#define BOOST_VARIANT_AUX_DECLARE_PARAMS \ |
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BOOST_PP_ENUM( \ |
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BOOST_VARIANT_LIMIT_TYPES \ |
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, BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL \ |
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, T \ |
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) \ |
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/**/ |
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/////////////////////////////////////////////////////////////////////////////// |
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// class template variant (concept inspired by Andrei Alexandrescu) |
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// |
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// Efficient, type-safe bounded discriminated union. |
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// |
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// Preconditions: |
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// - Each type must be unique. |
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// - No type may be const-qualified. |
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// |
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// Proper declaration form: |
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// variant<types> (where types is a type-sequence) |
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// or |
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// variant<T0,T1,...,Tn> (where T0 is NOT a type-sequence) |
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// |
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template < BOOST_VARIANT_AUX_DECLARE_PARAMS > class variant; |
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/////////////////////////////////////////////////////////////////////////////// |
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// metafunction make_recursive_variant |
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// |
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// Exposes a boost::variant with recursive_variant_ tags (below) substituted |
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// with the variant itself (wrapped as needed with boost::recursive_wrapper). |
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// |
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template < BOOST_VARIANT_AUX_DECLARE_PARAMS > struct make_recursive_variant; |
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#undef BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL |
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#undef BOOST_VARIANT_AUX_DECLARE_PARAMS |
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/////////////////////////////////////////////////////////////////////////////// |
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// type recursive_variant_ |
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// |
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// Tag type indicates where recursive variant substitution should occur. |
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// |
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#if !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT) |
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struct recursive_variant_ {}; |
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#else |
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typedef mpl::arg<1> recursive_variant_; |
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#endif |
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/////////////////////////////////////////////////////////////////////////////// |
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// metafunction make_variant_over |
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// |
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// Result is a variant w/ types of the specified type sequence. |
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// |
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template <typename Types> struct make_variant_over; |
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/////////////////////////////////////////////////////////////////////////////// |
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// metafunction make_recursive_variant_over |
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// |
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// Result is a recursive variant w/ types of the specified type sequence. |
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// |
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template <typename Types> struct make_recursive_variant_over; |
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} // namespace boost |
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#endif // BOOST_VARIANT_VARIANT_FWD_HPP
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