bug#4136: 23.1; delete-pair

[Lars Ingebrigtsen]

martin rudalics <rudalics@gmx.at> writes:

> Ne hlebom jedinnym.  Why can't we be generous and provide something like
> the attached?

The patch no longer applied, so I've respun it for Emacs 28 (included
below).

The thread here ended with Martin and Juri both agreeing that this was a
good idea, but it was never applied?

I don't use delete-pair myself regularly, but giving it some testing
now, this new version seems to work fine.

Any comments?  (The patch is 11 years old.)

diff --git a/lisp/emacs-lisp/lisp.el b/lisp/emacs-lisp/lisp.el
index 8c18557c79..ac4ba78897 100644
--- a/lisp/emacs-lisp/lisp.el
+++ b/lisp/emacs-lisp/lisp.el
@@ -735,12 +735,37 @@ insert-parentheses
   (insert-pair arg ?\( ?\)))
 
 (defun delete-pair (&optional arg)
-  "Delete a pair of characters enclosing ARG sexps following point.
-A negative ARG deletes a pair of characters around preceding ARG sexps."
-  (interactive "p")
-  (unless arg (setq arg 1))
-  (save-excursion (forward-sexp arg) (delete-char (if (> arg 0) -1 1)))
-  (delete-char (if (> arg 0) 1 -1)))
+  "Delete a pair of characters enclosing ARG sexps that follow point.
+A negative ARG deletes a pair around the preceding ARG sexps instead."
+  (interactive "P")
+  (if arg
+      (setq arg (prefix-numeric-value arg))
+    (setq arg 1))
+  (if (< arg 0)
+      (save-excursion
+       (skip-chars-backward " \t")
+       (save-excursion
+         (let ((close-char (char-before)))
+           (forward-sexp arg)
+           (unless (member (list (char-after) close-char)
+                           (mapcar (lambda (p)
+                                     (if (= (length p) 3) (cdr p) p))
+                                   insert-pair-alist))
+             (error "Not after matching pair"))
+           (delete-char 1)))
+       (delete-char -1))
+    (save-excursion
+      (skip-chars-forward " \t")
+      (save-excursion
+       (let ((open-char (char-after)))
+         (forward-sexp arg)
+         (unless (member (list open-char (char-before))
+                         (mapcar (lambda (p)
+                                   (if (= (length p) 3) (cdr p) p))
+                                 insert-pair-alist))
+           (error "Not before matching pair"))
+         (delete-char -1)))
+      (delete-char 1))))
 
 (defun raise-sexp (&optional arg)
   "Raise ARG sexps higher up the tree."


-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no