Subject: Re: bug#45199: 28.0.50; [PATCH] Make goto-char offer the number at point as default

From: Juri Linkov <[email-masked]>
Date: Sun, 20 Dec 2020 10:55:33 +0200

>> Shouldn't goto-line use the same function to read a number?
>> The first version of your patch used the code similar to
>> goto-line-read-args, so wouldn't it make sense to use the
>> new function in goto-line-read-args as well?
>
> Reusing it directly would be awkward, but goto-line-read-args could
> indeed use number-at-point.

Here's a patch where it uses number-at-point:

diff --git a/lisp/simple.el b/lisp/simple.el
index f79543058b..e17f2b0fc2 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1276,15 +1276,8 @@ goto-line-read-args
   (if (and current-prefix-arg (not (consp current-prefix-arg)))
       (list (prefix-numeric-value current-prefix-arg))
     ;; Look for a default, a number in the buffer at point.
-    (let* ((default
-             (save-excursion
-               (skip-chars-backward "0-9")
-               (if (looking-at "[0-9]")
-                   (string-to-number
-                    (buffer-substring-no-properties
-                     (point)
-                     (progn (skip-chars-forward "0-9")
-                            (point)))))))
+    (let* ((number (number-at-point))
+           (default (and (natnump number) number))
            ;; Decide if we're switching buffers.
            (buffer
             (if (consp current-prefix-arg)

Also this patch adds the same useful property from goto-line to goto-char.
When there is no number at point, then M-n gets the current char position
number for editing, so the user can decrease or increase it
relative to the current position:

diff --git a/lisp/subr.el b/lisp/subr.el
index 275e224b55..c7b7ac6444 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2828,7 +2828,7 @@ goto-char--read-natnum-interactive
       (list (prefix-numeric-value current-prefix-arg))
     (let* ((number (number-at-point))
            (default (and (natnump number) number)))
-      (list (read-number prompt default)))))
+      (list (read-number prompt (list default (point)))))))
 
 
 ;; Behind display-popup-menus-p test.