add reversed regexp

extra/regexp2/parser/parser.factor

@@ -30,7 +30,7 @@ SINGLETON: back-anchor INSTANCE: back-anchor node
 
 TUPLE: option-on option ; INSTANCE: option-on node
 TUPLE: option-off option ; INSTANCE: option-off node
-SINGLETONS: unix-lines dotall multiline comments case-insensitive unicode-case ;
+SINGLETONS: unix-lines dotall multiline comments case-insensitive unicode-case reversed-regexp ;
 
 SINGLETONS: letter-class LETTER-class Letter-class digit-class
 alpha-class non-newline-blank-class
@@ -49,9 +49,12 @@ left-parenthesis pipe caret dash ;
 : get-comments ( -- ? ) comments get-option ;
 : get-case-insensitive ( -- ? ) case-insensitive get-option ;
 : get-unicode-case ( -- ? ) unicode-case get-option ;
+: get-reversed-regexp ( -- ? ) reversed-regexp get-option ;
 
 : <negation> ( obj -- negation ) negation boa ;
-: <concatenation> ( seq -- concatenation ) >vector concatenation boa ;
+: <concatenation> ( seq -- concatenation )
+    >vector get-reversed-regexp [ reverse ] when
+    concatenation boa ;
 : <alternation> ( seq -- alternation ) >vector alternation boa ;
 : <capture-group> ( obj -- capture-group ) capture-group boa ;
 : <kleene-star> ( obj -- kleene-star ) kleene-star boa ;
@@ -76,7 +79,7 @@ left-parenthesis pipe caret dash ;
         2array [ [ from>> ] [ to>> ] bi < ] filter
         [ unmatchable-class ] [ first|alternation ] if-empty
     ] [
-        dup [ from>> ] [ to>> ] bi <
+        2dup <
         [ character-class-range boa ] [ 2drop unmatchable-class ] if
     ] if ;
 
@@ -109,6 +112,7 @@ ERROR: bad-option ch ;
         { CHAR: i [ case-insensitive ] }
         { CHAR: d [ unix-lines ] }
         { CHAR: m [ multiline ] }
+        { CHAR: r [ reversed-regexp ] }
         { CHAR: s [ dotall ] }
         { CHAR: u [ unicode-case ] }
         { CHAR: x [ comments ] }
@@ -345,13 +349,8 @@ DEFER: handle-left-bracket
     parse-character-class-first (parse-character-class) ;
 
 : finish-regexp-parse ( stack -- obj )
-    dup length {
-        { 1 [ first ] }
-        [
-            drop { pipe } split
-            [ first|concatenation ] map first|alternation
-        ]
-    } case ;
+    { pipe } split
+    [ first|concatenation ] map first|alternation ;
 
 : handle-right-parenthesis ( -- )
     stack beginning-of-group over last-index cut rest

extra/regexp2/regexp2-tests.factor

@@ -1,4 +1,5 @@
-USING: regexp2 tools.test kernel regexp2.parser regexp2.traversal ;
+USING: regexp2 tools.test kernel sequences regexp2.parser
+regexp2.traversal ;
 IN: regexp2-tests
 
 [ f ] [ "b" "a*" <regexp> matches? ] unit-test
@@ -248,6 +249,10 @@ IN: regexp2-tests
 [ f ] [ "A" "\\p{Lower}" <regexp> matches? ] unit-test
 [ t ] [ "A" "\\p{Lower}" <iregexp> matches? ] unit-test
 
+[ t ] [ "abc" <reversed> "abc" <rregexp> matches? ] unit-test
+[ t ] [ "abc" <reversed> "a[bB][cC]" <rregexp> matches? ] unit-test
+[ t ] [ "adcbe" "a(?r)(bcd)(?-r)e" <rregexp> matches? ] unit-test
+
 ! Bug in parsing word
 ! [ t ] [ "a" R' a' matches?  ] unit-test
 

extra/regexp2/regexp2.factor

@@ -41,6 +41,11 @@ IN: regexp2
     case-insensitive initial-option
     construct-regexp ;
 
+: <rregexp> ( string -- regexp )
+    default-regexp
+    reversed-regexp initial-option
+    construct-regexp ;
+
 : R! CHAR: ! <regexp> ; parsing
 : R" CHAR: " <regexp> ; parsing
 : R# CHAR: # <regexp> ; parsing