>From e4601d46bb5d5d1c721c22bf1f306748fdf1ed8a Mon Sep 17 00:00:00 2001
From: Mario Domenech Goulart <address@hidden>
Date: Sat, 11 Jan 2014 18:11:47 -0200
Subject: [PATCH] Fix bug in string-index-right and string-skip-right

Patch by David Van Horn to the SRFI-13 mailing list (see
http://srfi.schemers.org/srfi-13/post-mail-archive/msg00007.html).
Ported to CHICKEN by Seth Alves (see
http://lists.nongnu.org/archive/html/chicken-hackers/2014-01/msg00022.html).
---
 srfi-13.scm             |   12 ++++++------
 tests/srfi-13-tests.scm |   18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/srfi-13.scm b/srfi-13.scm
index 7b16153..876a2bd 100644
--- a/srfi-13.scm
+++ b/srfi-13.scm
@@ -1208,17 +1208,17 @@
   (let-string-start+end (start end) string-index-right str maybe-start+end
     (cond ((char? criteria)
 	   (let lp ((i (- end 1)))
-	     (and (>= i 0)
+	     (and (>= i start)
 		  (if (char=? criteria (string-ref str i)) i
 		      (lp (- i 1))))))
 	  ((char-set? criteria)
 	   (let lp ((i (- end 1)))
-	     (and (>= i 0)
+	     (and (>= i start)
 		  (if (char-set-contains? criteria (string-ref str i)) i
 		      (lp (- i 1))))))
 	  ((procedure? criteria)
 	   (let lp ((i (- end 1)))
-	     (and (>= i 0)
+	     (and (>= i start)
 		  (if (criteria (string-ref str i)) i
 		      (lp (- i 1))))))
 	  (else (##sys#error 'string-index-right "Second param is neither char-set, char, or predicate procedure."
@@ -1250,19 +1250,19 @@
   (let-string-start+end (start end) string-skip-right str maybe-start+end
     (cond ((char? criteria)
 	   (let lp ((i (- end 1)))
-	     (and (>= i 0)
+	     (and (>= i start)
 		  (if (char=? criteria (string-ref str i))
 		      (lp (- i 1))
 		      i))))
 	  ((char-set? criteria)
 	   (let lp ((i (- end 1)))
-	     (and (>= i 0)
+	     (and (>= i start)
 		  (if (char-set-contains? criteria (string-ref str i))
 		      (lp (- i 1))
 		      i))))
 	  ((procedure? criteria)
 	   (let lp ((i (- end 1)))
-	     (and (>= i 0)
+	     (and (>= i start)
 		  (if (criteria (string-ref str i)) (lp (- i 1))
 		      i))))
 	  (else (##sys#error 'string-skip-right "CRITERIA param is neither char-set or char."
diff --git a/tests/srfi-13-tests.scm b/tests/srfi-13-tests.scm
index 29d6b80..b10b8db 100644
--- a/tests/srfi-13-tests.scm
+++ b/tests/srfi-13-tests.scm
@@ -688,3 +688,21 @@
                 (handle-exceptions exn
                   (k #f)
                   (string=? "abrcaaba" (string-delete char-set:upper-case "abrAcaDabRa"))))))
+
+
+; http://srfi.schemers.org/srfi-13/post-mail-archive/msg00007.html
+; From: David Van Horn <address@hidden>
+; Date: Wed, 01 Nov 2006 07:53:34 +0100
+;
+; Both string-index-right and string-skip-right will continue to search
+; left past a given start index.
+;
+;    (string-index-right "abbb" #\a 1) ;; => 0, but should be #f
+;    (string-skip-right  "abbb" #\b 1) ;; => 0, but should be #f
+;
+; This also causes incorrect results for string-trim-right,
+; string-trim-both and string-tokenize when given a non-zero start
+; argument.
+
+(test "string-index-right" #f (string-index-right "abbb" #\a 1))
+(test "string-skip-right" #f (string-skip-right  "abbb" #\b 1))
-- 
1.7.10.4