117 lines
3.7 KiB
C++
117 lines
3.7 KiB
C++
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/*=============================================================================
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Copyright (c) 2001-2011 Joel de Guzman
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http://spirit.sourceforge.net/
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#ifndef BOOST_SPIRIT_MODIFY_OCTOBER_25_2008_0142PM
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#define BOOST_SPIRIT_MODIFY_OCTOBER_25_2008_0142PM
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/type_traits/is_base_of.hpp>
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#include <boost/spirit/home/support/unused.hpp>
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namespace boost { namespace spirit
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{
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template <typename Domain, typename T, typename Enable = void>
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struct is_modifier_directive;
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// Testing if a modifier set includes a modifier T involves
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// checking for inheritance (i.e. Modifiers is derived from T)
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template <typename Modifiers, typename T>
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struct has_modifier
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: is_base_of<T, Modifiers> {};
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// Adding modifiers is done using multi-inheritance
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template <typename Current, typename New, typename Enable = void>
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struct compound_modifier : Current, New
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{
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compound_modifier()
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: Current(), New() {}
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compound_modifier(Current const& current, New const& new_)
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: Current(current), New(new_) {}
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};
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// Don't add if New is already in Current
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template <typename Current, typename New>
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struct compound_modifier<
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Current, New, typename enable_if<has_modifier<Current, New> >::type>
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: Current
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{
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compound_modifier()
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: Current() {}
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compound_modifier(Current const& current, New const&)
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: Current(current) {}
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};
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// Special case if Current is unused_type
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template <typename New, typename Enable>
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struct compound_modifier<unused_type, New, Enable> : New
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{
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compound_modifier()
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: New() {}
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compound_modifier(unused_type, New const& new_)
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: New(new_) {}
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};
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// Domains may specialize this modify metafunction to allow
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// directives to add information to the Modifier template
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// parameter that is passed to the make_component metafunction.
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// By default, we return the modifiers untouched
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template <typename Domain, typename Enable = void>
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struct modify
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{
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typedef void proto_is_callable_;
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template <typename Sig>
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struct result;
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template <typename This, typename Tag, typename Modifiers>
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struct result<This(Tag, Modifiers)>
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{
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typedef typename remove_const<
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typename remove_reference<Tag>::type>::type
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tag_type;
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typedef typename remove_const<
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typename remove_reference<Modifiers>::type>::type
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modifiers_type;
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typedef typename mpl::if_<
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is_modifier_directive<Domain, tag_type>
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, compound_modifier<modifiers_type, tag_type>
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, Modifiers>::type
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type;
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};
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template <typename Tag, typename Modifiers>
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typename result<modify(Tag, Modifiers)>::type
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operator()(Tag tag, Modifiers modifiers) const
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{
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return op(tag, modifiers, is_modifier_directive<Domain, Tag>());
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}
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template <typename Tag, typename Modifiers>
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Modifiers
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op(Tag /*tag*/, Modifiers modifiers, mpl::false_) const
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{
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return modifiers;
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}
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template <typename Tag, typename Modifiers>
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compound_modifier<Modifiers, Tag>
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op(Tag tag, Modifiers modifiers, mpl::true_) const
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{
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return compound_modifier<Modifiers, Tag>(modifiers, tag);
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}
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};
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}}
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#endif
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