Fix fencepost error in highlighting of subexpressions.

diff --git a/v7/src/edwin/debug.scm b/v7/src/edwin/debug.scm
index 4c8703215fa4dbc648ae480f2deff77a9c5bce1c..8814d946358f9346b557f9401197a3f4a706bf01 100644 (file)
--- a/v7/src/edwin/debug.scm
+++ b/v7/src/edwin/debug.scm
@@ -1,6 +1,6 @@
 ;;; -*-Scheme-*-
 ;;;
-;;;    $Id: debug.scm,v 1.8 1993/08/13 01:22:17 jbank Exp $
+;;;    $Id: debug.scm,v 1.9 1993/08/13 01:56:57 jawilson Exp $
 ;;;
 ;;;    Copyright (c) 1992-93 Massachusetts Institute of Technology
 ;;;
@@ -116,10 +116,14 @@
            (highlight-region (horizontal-space-end start)
                              (horizontal-space-start lend))
            (loop (mark1+ lend)))
-         (highlight-region (horizontal-space-end start)
-                           (horizontal-space-start end))))))
+         (let ((start (horizontal-space-end start))
+               (end (horizontal-space-start end)))
+           (if (mark< start end)
+               (highlight-region start end)))))))
  
 (define (highlight-region start end)
+  (if (not (mark<= start end))
+      (error "Marks incorrectly related:" start end))
   (group-highlight (mark-group start) (mark-index start) (mark-index end)))
  
 (define (group-highlight group start end)