(string-prefix-p): New function.

2 files changed, 9 insertions, 0 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index e0125c85b73..d02dbadd9ca 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,7 @@
 2009-11-25  Stefan Monnier  <monnier@iro.umontreal.ca>
 
+        * subr.el (string-prefix-p): New function.
+
         * man.el (Man-completion-cache): New var.
         (Man-completion-table): Use it.
 
diff --git a/lisp/subr.el b/lisp/subr.el
index 2bc4c6b2bd2..9cbf4ab9ffc 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3193,6 +3193,13 @@ and replace a sub-expression, e.g.
       (setq matches (cons (substring string start l) matches)) ; leftover
       (apply #'concat (nreverse matches)))))
 
+(defun string-prefix-p (str1 str2 &optional ignore-case)
+  "Return non-nil if STR1 is a prefix of STR2.
+If IGNORE-CASE is non-nil, the comparison is done without paying attention
+to case differences."
+  (eq t (compare-strings str1 nil nil
+                         str2 0 (length str1) ignore-case)))
+
 ;;;; invisibility specs
 
 (defun add-to-invisibility-spec (element)