From 7724ad2387e355888e6607ede810c0776a37a573 Mon Sep 17 00:00:00 2001
From: Doug Coleman <doug.coleman@gmail.com>
Date: Sat, 13 Sep 2008 18:20:38 -0500
Subject: [PATCH] allow |b  b| || regexps

---
 unfinished/regexp2/parser/parser-tests.factor | 4 ++++
 unfinished/regexp2/parser/parser.factor       | 2 +-
 unfinished/regexp2/regexp2-tests.factor       | 7 +++++++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/unfinished/regexp2/parser/parser-tests.factor b/unfinished/regexp2/parser/parser-tests.factor
index 9dc7dc7909..6911e8e76d 100644
--- a/unfinished/regexp2/parser/parser-tests.factor
+++ b/unfinished/regexp2/parser/parser-tests.factor
@@ -31,3 +31,7 @@ IN: regexp2.parser
 [ ] [ "[a-c]" test-regexp ] unit-test
 [ ] [ "[^a-c]" test-regexp ] unit-test
 [ "[^]" test-regexp ] must-fail
+
+[ ] [ "|b" test-regexp ] unit-test
+[ ] [ "b|" test-regexp ] unit-test
+[ ] [ "||" test-regexp ] unit-test
diff --git a/unfinished/regexp2/parser/parser.factor b/unfinished/regexp2/parser/parser.factor
index a970f82aab..fb1bd08bfe 100644
--- a/unfinished/regexp2/parser/parser.factor
+++ b/unfinished/regexp2/parser/parser.factor
@@ -67,7 +67,7 @@ left-parenthesis pipe caret dash ;
 : <negation> ( obj -- negation ) negation boa ;
 : <concatenation> ( seq -- concatenation )
     >vector get-reversed-regexp [ reverse ] when
-    concatenation boa ;
+    [ epsilon ] [ concatenation boa ] if-empty ;
 : <alternation> ( seq -- alternation ) >vector alternation boa ;
 : <capture-group> ( obj -- capture-group ) capture-group boa ;
 : <kleene-star> ( obj -- kleene-star ) kleene-star boa ;
diff --git a/unfinished/regexp2/regexp2-tests.factor b/unfinished/regexp2/regexp2-tests.factor
index f691c2becf..e77a7a4419 100644
--- a/unfinished/regexp2/regexp2-tests.factor
+++ b/unfinished/regexp2/regexp2-tests.factor
@@ -14,6 +14,13 @@ IN: regexp2-tests
 [ t ] [ "c" "a|b|c" <regexp> matches? ] unit-test
 [ f ] [ "c" "d|e|f" <regexp> matches? ] unit-test
 
+[ t ] [ "b" "|b" <regexp> matches? ] unit-test
+[ t ] [ "b" "b|" <regexp> matches? ] unit-test
+[ t ] [ "" "b|" <regexp> matches? ] unit-test
+[ t ] [ "" "b|" <regexp> matches? ] unit-test
+[ f ] [ "" "|" <regexp> matches? ] unit-test
+[ f ] [ "" "|||||||" <regexp> matches? ] unit-test
+
 [ f ] [ "aa" "a|b|c" <regexp> matches? ] unit-test
 [ f ] [ "bb" "a|b|c" <regexp> matches? ] unit-test
 [ f ] [ "cc" "a|b|c" <regexp> matches? ] unit-test