Chris@16: //-----------------------------------------------------------------------------
Chris@16: // boost variant/detail/apply_visitor_unary.hpp header file
Chris@16: // See http://www.boost.org for updates, documentation, and revision history.
Chris@16: //-----------------------------------------------------------------------------
Chris@16: //
Chris@101: // Copyright (c) 2002-2003 Eric Friedman
Chris@101: // Copyright (c) 2014 Antony Polukhin
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_VARIANT_DETAIL_APPLY_VISITOR_UNARY_HPP
Chris@16: #define BOOST_VARIANT_DETAIL_APPLY_VISITOR_UNARY_HPP
Chris@16: 
Chris@16: #include "boost/config.hpp"
Chris@16: #include "boost/detail/workaround.hpp"
Chris@16: #include "boost/variant/detail/generic_result_type.hpp"
Chris@16: 
Chris@16: #if BOOST_WORKAROUND(__EDG__, BOOST_TESTED_AT(302))
Chris@101: #include "boost/core/enable_if.hpp"
Chris@16: #include "boost/mpl/not.hpp"
Chris@16: #include "boost/type_traits/is_const.hpp"
Chris@16: #endif
Chris@16: 
Chris@101: #if !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
Chris@101: #   include <boost/mpl/distance.hpp>
Chris@101: #   include <boost/mpl/advance.hpp>
Chris@101: #   include <boost/mpl/deref.hpp>
Chris@101: #   include <boost/mpl/size.hpp>
Chris@101: #   include <boost/utility/declval.hpp>
Chris@101: #   include <boost/core/enable_if.hpp>
Chris@101: #   include "boost/variant/detail/has_result_type.hpp"
Chris@101: #endif
Chris@101: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: //////////////////////////////////////////////////////////////////////////
Chris@16: // function template apply_visitor(visitor, visitable)
Chris@16: //
Chris@16: // Visits visitable with visitor.
Chris@16: //
Chris@16: 
Chris@16: //
Chris@16: // nonconst-visitor version:
Chris@16: //
Chris@16: 
Chris@16: #if !BOOST_WORKAROUND(__EDG__, BOOST_TESTED_AT(302))
Chris@16: 
Chris@16: #   define BOOST_VARIANT_AUX_APPLY_VISITOR_NON_CONST_RESULT_TYPE(V) \
Chris@16:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename V::result_type) \
Chris@16:     /**/
Chris@16: 
Chris@16: #else // EDG-based compilers
Chris@16: 
Chris@16: #   define BOOST_VARIANT_AUX_APPLY_VISITOR_NON_CONST_RESULT_TYPE(V) \
Chris@16:     typename enable_if< \
Chris@16:           mpl::not_< is_const< V > > \
Chris@16:         , BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename V::result_type) \
Chris@16:         >::type \
Chris@16:     /**/
Chris@16: 
Chris@16: #endif // EDG-based compilers workaround
Chris@16: 
Chris@16: template <typename Visitor, typename Visitable>
Chris@16: inline
Chris@16:     BOOST_VARIANT_AUX_APPLY_VISITOR_NON_CONST_RESULT_TYPE(Visitor)
Chris@16: apply_visitor(Visitor& visitor, Visitable& visitable)
Chris@16: {
Chris@16:     return visitable.apply_visitor(visitor);
Chris@16: }
Chris@16: 
Chris@16: #undef BOOST_VARIANT_AUX_APPLY_VISITOR_NON_CONST_RESULT_TYPE
Chris@16: 
Chris@16: //
Chris@16: // const-visitor version:
Chris@16: //
Chris@16: 
Chris@16: template <typename Visitor, typename Visitable>
Chris@16: inline
Chris@16:     BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@16: apply_visitor(const Visitor& visitor, Visitable& visitable)
Chris@16: {
Chris@16:     return visitable.apply_visitor(visitor);
Chris@16: }
Chris@16: 
Chris@101: 
Chris@101: #if !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
Chris@101: 
Chris@101: // C++14
Chris@101: namespace detail { namespace variant {
Chris@101: 
Chris@101: // This class serves only metaprogramming purposes. none of its methods must be called at runtime!
Chris@101: template <class Visitor, class Variant>
Chris@101: struct result_multideduce1 {
Chris@101:     typedef typename Variant::types                 types;
Chris@101:     typedef typename boost::mpl::begin<types>::type begin_it;
Chris@101:     typedef typename boost::mpl::advance<
Chris@101:         begin_it, boost::mpl::int_<boost::mpl::size<types>::type::value - 1>
Chris@101:     >::type                                         last_it;
Chris@101: 
Chris@101:     // For metaprogramming purposes ONLY! Do not use this method (and class) at runtime!
Chris@101:     static Visitor& vis() BOOST_NOEXCEPT {
Chris@101:         // Functions that work with lambdas must be defined in same translation unit.
Chris@101:         // Because of that, we can not use `boost::decval<Visitor&>()` here.
Chris@101:         Visitor&(*f)() = 0; // pointer to function
Chris@101:         return f();
Chris@101:     }
Chris@101: 
Chris@101:     static decltype(auto) deduce_impl(last_it, unsigned /*helper*/) {
Chris@101:         typedef typename boost::mpl::deref<last_it>::type value_t;
Chris@101:         return vis()( boost::declval< value_t& >() );
Chris@101:     }
Chris@101: 
Chris@101:     template <class It>
Chris@101:     static decltype(auto) deduce_impl(It, unsigned helper) {
Chris@101:         typedef typename boost::mpl::next<It>::type next_t;
Chris@101:         typedef typename boost::mpl::deref<It>::type value_t;
Chris@101:         if (helper == boost::mpl::distance<begin_it, It>::type::value) {
Chris@101:             return deduce_impl(next_t(), ++helper);
Chris@101:         }
Chris@101: 
Chris@101:         return vis()( boost::declval< value_t& >() );
Chris@101:     }
Chris@101: 
Chris@101:     static decltype(auto) deduce() {
Chris@101:         return deduce_impl(begin_it(), 0);
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: template <class Visitor, class Variant>
Chris@101: struct result_wrapper1
Chris@101: {
Chris@101:     typedef decltype(result_multideduce1<Visitor, Variant>::deduce()) result_type;
Chris@101: 
Chris@101:     Visitor& visitor_;
Chris@101:     explicit result_wrapper1(Visitor& visitor) BOOST_NOEXCEPT
Chris@101:         : visitor_(visitor)
Chris@101:     {}
Chris@101: 
Chris@101:     template <class T>
Chris@101:     result_type operator()(T& val) const {
Chris@101:         return visitor_(val);
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: }} // namespace detail::variant
Chris@101: 
Chris@101: template <typename Visitor, typename Visitable>
Chris@101: inline decltype(auto) apply_visitor(Visitor& visitor, Visitable& visitable,
Chris@101:     typename boost::disable_if<
Chris@101:         boost::detail::variant::has_result_type<Visitor>
Chris@101:     >::type* = 0)
Chris@101: {
Chris@101:     boost::detail::variant::result_wrapper1<Visitor, Visitable> cpp14_vis(visitor);
Chris@101:     return visitable.apply_visitor(cpp14_vis);
Chris@101: }
Chris@101: 
Chris@101: template <typename Visitor, typename Visitable>
Chris@101: inline decltype(auto) apply_visitor(const Visitor& visitor, Visitable& visitable,
Chris@101:     typename boost::disable_if<
Chris@101:         boost::detail::variant::has_result_type<Visitor>
Chris@101:     >::type* = 0)
Chris@101: {
Chris@101:     boost::detail::variant::result_wrapper1<const Visitor, Visitable> cpp14_vis(visitor);
Chris@101:     return visitable.apply_visitor(cpp14_vis);
Chris@101: }
Chris@101: 
Chris@101: #endif // !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_VARIANT_DETAIL_APPLY_VISITOR_UNARY_HPP