| /*============================================================================= |
| Copyright (c) 2001-2010 Joel de Guzman |
| http://spirit.sourceforge.net/ |
| |
| 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_SPIRIT_MODIFY_OCTOBER_25_2008_0142PM |
| #define BOOST_SPIRIT_MODIFY_OCTOBER_25_2008_0142PM |
| |
| #if defined(_MSC_VER) |
| #pragma once |
| #endif |
| |
| #include <boost/proto/proto.hpp> |
| #include <boost/mpl/if.hpp> |
| #include <boost/type_traits/is_base_of.hpp> |
| #include <boost/spirit/home/support/unused.hpp> |
| |
| namespace boost { namespace spirit |
| { |
| template <typename Domain, typename T, typename Enable = void> |
| struct is_modifier_directive; |
| |
| // Testing if a modifier set includes a modifier T involves |
| // checking for inheritance (i.e. Modifiers is derived from T) |
| template <typename Modifiers, typename T> |
| struct has_modifier |
| : is_base_of<T, Modifiers> {}; |
| |
| // Adding modifiers is done using multi-inheritance |
| template <typename Current, typename New, typename Enable = void> |
| struct compound_modifier : Current, New |
| { |
| compound_modifier() |
| : Current(), New() {} |
| |
| compound_modifier(Current const& current, New const& new_) |
| : Current(current), New(new_) {} |
| }; |
| |
| // Don't add if New is already in Current |
| template <typename Current, typename New> |
| struct compound_modifier< |
| Current, New, typename enable_if<has_modifier<Current, New> >::type> |
| : Current |
| { |
| compound_modifier() |
| : Current() {} |
| |
| compound_modifier(Current const& current, New const&) |
| : Current(current) {} |
| }; |
| |
| // Special case if Current is unused_type |
| template <typename New, typename Enable> |
| struct compound_modifier<unused_type, New, Enable> : New |
| { |
| compound_modifier() |
| : New() {} |
| |
| compound_modifier(unused_type, New const& new_) |
| : New(new_) {} |
| }; |
| |
| // Domains may specialize this modify metafunction to allow |
| // directives to add information to the Modifier template |
| // parameter that is passed to the make_component metafunction. |
| // By default, we return the modifiers untouched |
| template <typename Domain, typename Enable = void> |
| struct modify |
| { |
| template <typename Sig> |
| struct result; |
| |
| template <typename This, typename Tag, typename Modifiers> |
| struct result<This(Tag, Modifiers)> |
| { |
| typedef typename remove_const< |
| typename remove_reference<Tag>::type>::type |
| tag_type; |
| typedef typename remove_const< |
| typename remove_reference<Modifiers>::type>::type |
| modifiers_type; |
| |
| typedef typename mpl::if_< |
| is_modifier_directive<Domain, tag_type> |
| , compound_modifier<modifiers_type, tag_type> |
| , Modifiers>::type |
| type; |
| }; |
| |
| template <typename Tag, typename Modifiers> |
| typename result<modify(Tag, Modifiers)>::type |
| operator()(Tag tag, Modifiers modifiers) const |
| { |
| return op(tag, modifiers, is_modifier_directive<Domain, Tag>()); |
| } |
| |
| template <typename Tag, typename Modifiers> |
| Modifiers |
| op(Tag /*tag*/, Modifiers modifiers, mpl::false_) const |
| { |
| return modifiers; |
| } |
| |
| template <typename Tag, typename Modifiers> |
| compound_modifier<Modifiers, Tag> |
| op(Tag tag, Modifiers modifiers, mpl::true_) const |
| { |
| return compound_modifier<Modifiers, Tag>(modifiers, tag); |
| } |
| }; |
| }} |
| |
| namespace boost { namespace proto |
| { |
| template <typename Domain, typename Enable> |
| struct is_callable<spirit::modify<Domain, Enable> > |
| : mpl::true_ {}; |
| }} |
| |
| #endif |