(looking-back): New function to check for regular expression before point.

1 files changed, 13 insertions, 0 deletions

diff --git a/lisp/subr.el b/lisp/subr.el
index c03b2ff0a98..2ca79e54b76 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1820,6 +1820,19 @@ STRING should be given if the last search was by `string-match' on STRING."
         (buffer-substring-no-properties (match-beginning num)
                                         (match-end num)))))
 
+(defun looking-back (regexp)
+  "Return t if text before point matches regular expression REGEXP.
+This function modifies the match data that `match-beginning',
+`match-end' and `match-data' access; save and restore the match
+data if you want to preserve them."
+  (save-excursion
+    (let ((beg (point)))
+      (if (re-search-backward regexp nil t)
+          (if (= (match-end 0) beg)
+              t
+            nil)
+        nil))))
+
 (defconst split-string-default-separators "[ \f\t\n\r\v]+"
   "The default value of separators for `split-string'.