97 lines
3.2 KiB
C++
97 lines
3.2 KiB
C++
/*
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* Copyright 2019 by its authors. See AUTHORS.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef EOLIAN_CXX_CONTEXT_HH
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#define EOLIAN_CXX_CONTEXT_HH
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namespace efl { namespace eolian { namespace grammar {
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struct context_null {};
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template <typename Tag, typename Tail = context_null>
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struct context_cons
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{
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typename std::remove_reference<Tag>::type const tag;
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typename std::remove_reference<Tail>::type const tail;
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};
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template <typename NewTag, typename Tag, typename Tail>
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constexpr context_cons<NewTag, context_cons<Tag, Tail>>
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context_add_tag(NewTag const& tag, context_cons<Tag, Tail> const& context)
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{
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return context_cons<NewTag, context_cons<Tag, Tail>>{tag, context};
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}
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template <typename NewTag>
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constexpr context_cons<NewTag, context_null>
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context_add_tag(NewTag const& tag, context_null context)
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{
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return context_cons<NewTag, context_null>{tag, context};
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}
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template <typename Tag, typename Tail>
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constexpr context_cons<Tag, Tail>
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context_replace_tag(Tag const& tag, context_cons<Tag, Tail> const& context)
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{
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return {tag, context.tail};
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}
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template <typename Tag>
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constexpr context_cons<Tag, context_null>
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context_replace_tag(Tag const& tag, context_null const&)
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{
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return context_cons<Tag, context_null>{tag, context_null{}};
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}
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template <typename Tag, typename OtherTag, typename Tail>
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constexpr context_cons<OtherTag, decltype(context_replace_tag(std::declval<Tag>(), std::declval<Tail>()))>
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context_replace_tag(Tag const& tag, context_cons<OtherTag, Tail> const& context)
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{
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return {context.tag, context_replace_tag(tag, context.tail)};
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}
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template <typename Tag, typename Context>
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struct tag_check;
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template <typename Tag, typename Tail>
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struct tag_check<Tag, context_cons<Tag, Tail>> : std::true_type {};
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template <typename Tag>
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struct tag_check<Tag, context_null> : std::false_type {};
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template <typename Tag, typename OtherTag, typename Context>
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struct tag_check<Tag, context_cons<OtherTag, Context>> : tag_check<Tag, Context> {};
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template <typename Tag, typename SameTag, typename Tail>
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constexpr Tag const& context_find_tag(context_cons<SameTag, Tail> const& context
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, typename std::enable_if<std::is_same<Tag, SameTag>::value>::type* = nullptr)
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{
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return context.tag;
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}
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template <typename Tag, typename OtherTag, typename Tail>
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constexpr Tag const& context_find_tag(context_cons<OtherTag, Tail> const& context
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, typename std::enable_if<!std::is_same<Tag, OtherTag>::value>::type* = nullptr)
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{
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return context_find_tag<Tag>(context.tail);
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}
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template <typename Tag>
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constexpr Tag const& context_find_tag(context_null const& context)
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{
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static_assert(std::is_same<Tag, context_null>::value, "Tag type not available in this generation context");
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return context;
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}
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} } }
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#endif
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