67 lines
1.9 KiB
C++
67 lines
1.9 KiB
C++
#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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Tag tag;
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Tail const& tail;
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};
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template <typename Tag>
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struct context_cons<Tag, context_null>
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{
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Tag tag;
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context_null tail;
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};
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template <typename NewTag, typename Tag, typename Tail>
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context_cons<NewTag, context_cons<Tag, Tail>>
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context_add_tag(NewTag 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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context_cons<NewTag, context_null>
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context_add_tag(NewTag 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 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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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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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, typename OtherTag, typename Tail>
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Tag const& context_find_tag(context_null const& context)
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{
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throw std::logic_error("Context for generation not available");
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}
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} } }
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#endif
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