Reject reversed ranges like [z-a].

2 files changed, 11 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 4f98cba..7a8e7e2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2014-03-17  Kaz Kylheku  <kaz@kylheku.com>
 
+	* awkreg.awk (eat_bracket_exp): Capture the endpoint characters of a
+	range into the variables x and y, and use these to assert that
+	the lower endpoint is not lexicographically above the upper endpoint.
+
+2014-03-17  Kaz Kylheku  <kaz@kylheku.com>
+
 	* awkreg.awk (driver): fix references to nonexistent variable ir;
 	should be ok.
 
diff --git a/awkreg.awk b/awkreg.awk
index 52c8353..043d44a 100644
--- a/awkreg.awk
+++ b/awkreg.awk
@@ -97,7 +97,7 @@ function eat_class(c)
 
 function eat_bracket_exp(e,
                          #local
-                         f, o)
+                         f, o, x, y)
 {
   o = e
   e = eat_char(e)
@@ -115,6 +115,7 @@ function eat_bracket_exp(e,
       continue
     }
 
+    x = substr(e, 1, 1);
     f = eat_bchar(e)
 
     if (f == e)
@@ -123,8 +124,10 @@ function eat_bracket_exp(e,
 
     if (matches(e, "-")) {
       e = eat_char(e)
+      y = substr(e, 1, 1);
       f = eat_bchar(e)
-      if (f == e)
+
+      if (x > y || f == e)
         return o
       e = f
     }