Merge pull request #258 from hanickadot/lookbehind

support for look behind

include/ctll/list.hpp

@@ -47,6 +47,14 @@ template <typename T = _nothing> constexpr auto pop_and_get_front(empty_list, T
 template <typename Head, typename... As, typename T = _nothing> constexpr auto front(list<Head, As...>, T = T()) noexcept -> Head { return {}; }
 template <typename T = _nothing> constexpr auto front(empty_list, T = T()) noexcept -> T { return {}; }
 
+// rotate list
+template <typename T> struct rotate_item {
+	template <typename... Ts> friend constexpr auto operator+(list<Ts...>, rotate_item<T>) noexcept -> list<T, Ts...> { return {}; }
+};
+
+template <typename... Ts> constexpr auto rotate(list<Ts...>) -> decltype((list<>{} + ... + rotate_item<Ts>{})) {
+	return {};
+}
 
 // set operations
 template <typename T> struct item_matcher {

include/ctre/actions/look.inc.hpp

@@ -31,4 +31,38 @@ template <auto V, typename... Look, typename... Ts, size_t Counter> static const
 	return pcre_context{ctll::list<lookahead_negative<Look...>, Ts...>(), pcre_parameters<Counter>()};
 }
 
+// LOOKBEHIND
+
+// lookbehind positive start
+template <auto V, typename... Ts, size_t Counter> static constexpr auto apply(pcre::start_lookbehind_positive, ctll::term<V>, pcre_context<ctll::list<Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<look_start<lookbehind_positive<>>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookbehind positive end
+template <auto V, typename Look, typename... Ts, size_t Counter> static constexpr auto apply(pcre::look_finish, ctll::term<V>, pcre_context<ctll::list<Look, look_start<lookbehind_positive<>>, Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<lookbehind_positive<decltype(ctre::rotate_for_lookbehind::rotate(Look{}))>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookbehind positive end (sequence)
+template <auto V, typename... Look, typename... Ts, size_t Counter> static constexpr auto apply(pcre::look_finish, ctll::term<V>, pcre_context<ctll::list<ctre::sequence<Look...>, look_start<lookbehind_positive<>>, Ts...>, pcre_parameters<Counter>>) {
+	using my_lookbehind = decltype(ctre::convert_to_basic_list<lookbehind_positive>(ctll::rotate(ctll::list<decltype(ctre::rotate_for_lookbehind::rotate(Look{}))...>{})));
+	return pcre_context{ctll::list<my_lookbehind, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookbehind negative start
+template <auto V, typename... Ts, size_t Counter> static constexpr auto apply(pcre::start_lookbehind_negative, ctll::term<V>, pcre_context<ctll::list<Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<look_start<lookbehind_negative<>>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookbehind negative end
+template <auto V, typename Look, typename... Ts, size_t Counter> static constexpr auto apply(pcre::look_finish, ctll::term<V>, pcre_context<ctll::list<Look, look_start<lookbehind_negative<>>, Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<lookbehind_negative<decltype(ctre::rotate_for_lookbehind::rotate(Look{}))>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookbehind negative end (sequence)
+template <auto V, typename... Look, typename... Ts, size_t Counter> static constexpr auto apply(pcre::look_finish, ctll::term<V>, pcre_context<ctll::list<ctre::sequence<Look...>, look_start<lookbehind_negative<>>, Ts...>, pcre_parameters<Counter>>) {
+	using my_lookbehind = decltype(ctre::convert_to_basic_list<lookbehind_negative>(ctll::rotate(ctll::list<decltype(ctre::rotate_for_lookbehind::rotate(Look{}))...>{})));
+	return pcre_context{ctll::list<my_lookbehind, Ts...>(), pcre_parameters<Counter>()};
+}
+
 #endif

include/ctre/atoms.hpp

@@ -13,6 +13,7 @@ struct start_mark { };
 struct end_mark { };
 struct end_cycle_mark { };
 struct end_lookahead_mark { };
+struct end_lookbehind_mark { };
 template <size_t Id> struct numeric_mark { };
 
 struct any { };
@@ -51,6 +52,9 @@ template <typename Type> struct look_start { };
 template <typename... Content> struct lookahead_positive { };
 template <typename... Content> struct lookahead_negative { };
 
+template <typename... Content> struct lookbehind_positive { };
+template <typename... Content> struct lookbehind_negative { };
+
 struct atomic_start { };
 
 template <typename... Content> struct atomic_group { };

include/ctre/first.hpp

@@ -161,6 +161,18 @@ constexpr auto first(ctll::list<Content...>, ctll::list<lookahead_positive<Seq..
 	return ctll::list<can_be_anything>{};
 }
 
+// lookbehind_negative TODO fixme
+template <typename... Content, typename... Seq, typename... Tail> 
+constexpr auto first(ctll::list<Content...>, ctll::list<lookbehind_negative<Seq...>, Tail...>) noexcept {
+	return ctll::list<can_be_anything>{};
+}
+
+// lookbehind_positive
+template <typename... Content, typename... Seq, typename... Tail> 
+constexpr auto first(ctll::list<Content...>, ctll::list<lookbehind_positive<Seq...>, Tail...>) noexcept {
+	return ctll::list<can_be_anything>{};
+}
+
 // lookahead_negative TODO fixme
 template <typename... Content, typename... Seq, typename... Tail> 
 constexpr auto first(ctll::list<Content...>, ctll::list<lookahead_negative<Seq...>, Tail...>) noexcept {

include/ctre/pcre.gram

@@ -67,10 +67,12 @@ number2->epsilon | num,[push_number],<number2>
 preblock->open,[prepare_capture],<block>
 
 block-><content_in_capture>,[make_capture],close
-block->questionmark,[reset_capture],angle_close,[start_atomic],<content_in_capture>,[make_atomic],close
-block->questionmark,[reset_capture],equal_sign,[start_lookahead_positive],<content_in_capture>,[look_finish],close
-block->questionmark,[reset_capture],exclamation_mark,[start_lookahead_negative],<content_in_capture>,[look_finish],close
-block->questionmark,[reset_capture],colon,<content_in_capture>,close
+block->questionmark,angle_close,[reset_capture],[start_atomic],<content_in_capture>,[make_atomic],close
+block->questionmark,equal_sign,[reset_capture],[start_lookahead_positive],<content_in_capture>,[look_finish],close
+block->questionmark,angle_open,equal_sign,[reset_capture],[start_lookbehind_positive],<content_in_capture>,[look_finish],close
+block->questionmark,exclamation_mark,[reset_capture],[start_lookahead_negative],<content_in_capture>,[look_finish],close
+block->questionmark,angle_open,exclamation_mark,[reset_capture],[start_lookbehind_negative],<content_in_capture>,[look_finish],close
+block->questionmark,colon,[reset_capture],<content_in_capture>,close
 block->questionmark,angle_open,<block_name>,angle_close,<content_in_capture>,[make_capture_with_name],close
 
 block_name->alpha_characters,[push_name],<block_name2>