lookahead support (part 1)

Author: Hana Dusíková

include/ctre/actions/look.inc.hpp

@@ -0,0 +1,34 @@
+#ifndef CTRE__ACTIONS__LOOKAHEAD__HPP
+#define CTRE__ACTIONS__LOOKAHEAD__HPP
+
+// lookahead positive start
+template <auto V, typename... Ts, size_t Counter> static constexpr auto apply(pcre::start_lookahead_positive, ctll::term<V>, pcre_context<ctll::list<Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<look_start<lookahead_positive<>>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookahead 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<lookahead_positive<>>, Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<lookahead_positive<Look>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookahead 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<lookahead_positive<>>, Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<lookahead_positive<Look...>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookahead negative start
+template <auto V, typename... Ts, size_t Counter> static constexpr auto apply(pcre::start_lookahead_negative, ctll::term<V>, pcre_context<ctll::list<Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<look_start<lookahead_negative<>>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookahead 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<lookahead_negative<>>, Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<lookahead_negative<Look>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+// lookahead 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<lookahead_negative<>>, Ts...>, pcre_parameters<Counter>>) {
+	return pcre_context{ctll::list<lookahead_negative<Look...>, Ts...>(), pcre_parameters<Counter>()};
+}
+
+#endif

include/ctre/atoms.hpp

@@ -10,6 +10,7 @@ struct accept { };
 struct start_mark { };
 struct end_mark { };
 struct end_cycle_mark { };
+struct end_lookahead_mark { };
 template <size_t Id> struct numeric_mark { };
 
 // actual AST of regexp
@@ -39,10 +40,14 @@ template <size_t Index, typename Name, typename... Content> struct capture_with_
 
 template <size_t Index> struct back_reference { };
 template <typename Name> struct back_reference_with_name { };
- 
+
+template <typename Type> struct look_start { };
+
+template <typename... Content> struct lookahead_positive { };
+template <typename... Content> struct lookahead_negative { };
 
 struct assert_begin { };
- struct assert_end { };
+struct assert_end { };
 
 }
 

include/ctre/evaluation.hpp

@@ -145,7 +145,6 @@ constexpr CTRE_FORCE_INLINE R evaluate(const Iterator begin, Iterator current, c
 	} else {
 		return evaluate(begin, current, end, captures, ctll::list<HeadContent, Tail...>());
 	}
-	
 }
 
 // matching empty in patterns
@@ -361,6 +360,34 @@ constexpr CTRE_FORCE_INLINE R evaluate(const Iterator begin, Iterator current, c
 	return not_matched;
 }
 
+// end of lookahead
+template <typename R, typename Iterator, typename EndIterator, typename... Tail> 
+constexpr CTRE_FORCE_INLINE R evaluate(const Iterator, Iterator current, const EndIterator, R captures, ctll::list<end_lookahead_mark>) noexcept {
+	return captures.set_end_mark(current).matched();
+}
+
+// lookahead positive
+template <typename R, typename Iterator, typename EndIterator, typename... Content, typename... Tail> 
+constexpr CTRE_FORCE_INLINE R evaluate(const Iterator begin, Iterator current, const EndIterator end, R captures, ctll::list<lookahead_positive<Content...>, Tail...>) noexcept {
+	
+	if (auto lookahead_result = evaluate(begin, current, end, captures, ctll::list<sequence<Content...>, end_lookahead_mark>())) {
+		captures = lookahead_result.unmatch();
+		return evaluate(begin, current, end, captures, ctll::list<Tail...>());
+	} else {
+		return not_matched;
+	}
+}
+
+// lookahead negative
+template <typename R, typename Iterator, typename EndIterator, typename... Content, typename... Tail> 
+constexpr CTRE_FORCE_INLINE R evaluate(const Iterator begin, Iterator current, const EndIterator end, R captures, ctll::list<lookahead_negative<Content...>, Tail...>) noexcept {
+	
+	if (auto lookahead_result = evaluate(begin, current, end, captures, ctll::list<sequence<Content...>, end_lookahead_mark>())) {
+		return not_matched;
+	} else {
+		return evaluate(begin, current, end, captures, ctll::list<Tail...>());
+	}
+}
 
 }
 

include/ctre/pcre.gram

@@ -18,12 +18,14 @@ caret={^}
 minus={-}
 angle_open={<}
 angle_close={>}
+equal_sign={=}
+exclamation_mark={!}
 
 escape_alphanum={b,c,h,i,j,k,l,m,o,p,q,v,y,z,A,B,C,E,F,G,H,I,J,K,L,M,O,P,Q,U,V,X,Y,Z,1,2,3,4,5,6,7,8,9}
 hexdec={0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,A,B,C,D,E,F}
 octal={0,1,2,3,4,5,6,7}
-nonspecial_characters={a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,0,1,2,3,4,5,6,7,8,9,\,,:}
-nonspecial_characters_in_class={_,+,*,(,),.,$,\{,\},?}
+nonspecial_characters={a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,0,1,2,3,4,5,6,7,8,9,\,,:,!,=}
+nonspecial_characters_in_class={_,+,*,(,),.,$,\{,\},?,!,=}
 alpha_characters={a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,_}
 alphanum_characters={a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,0,1,2,3,4,5,6,7,8,9,_}
 set_control_chars={:,],-}
@@ -60,6 +62,8 @@ number2->epsilon | num,[push_number],<number2>
 preblock->open,[prepare_capture],<block>
 
 block-><content_in_capture>,[make_capture],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_open,<block_name>,angle_close,<content_in_capture>,[make_capture_with_name],close