Re: help with regexp function

[Stephen Berman]

On Tue, 21 Nov 2017 17:30:15 -0600 "B. T. Raven" <btraven@nihilo.net> wrote:

> Dear Emacs gurus:
>
> I can perform this inteactive substitution
> CM-%: \(^[0-9]+ \)\(.+\) -> \2 \1)
> in order to change a buffer line prefixed with a number into one post-fixed
> with the same number but I can't figue out how to do the same programatically
> to a whole region. I started with this code:
>
> (defun verse-num-move-beg-to-end (beg end)
> "Move int-string and following space from beginning of line to end of line
> throughout region."
> (interactive "r")
> (goto-char beg)
> (while (<= (point) end)
>    (re-search-forward "^[0-9]+ ")
>    (setq num (substring (match-string 0) 0 -1)) ;; should be a string of
> ;;digits without trailing space
>    (print num)

Here's a pretty direct translation of the interactive substitution:

(defun verse-num-move-beg-to-end (beg end)
  "Move int-string and following space from beginning of line to
end of line throughout region."
  (interactive "r")
  (goto-char beg)
  (while (<= (point) end)
    (re-search-forward "^\\([0-9]+\\) \\(.*\\)$")
    (replace-match (concat (match-string 2) " " (match-string 1) ")"))))

> ;; here the value generates a wrong argument error:
> setq: Wrong type argument: listp, #("234" 0 3 (fontified t))
> (type-of  #("234" 0 3 (fontified t)))

I can't tell what the problem without seeing the code that causes it.
Were you trying to treat the propertized string as a list because of the
#(...) notation?

> ;; I have a function which is a black box to to me but it works in the larger
> context I have it in. Does match-string do something like this implicitly
> (casting a list as a string?)

Not AFAIK.

> (substring (match-string 0) 0 -1)
> (replace-match "" nil t)
>
>
> 234 asentuhasneothu ;; example buffer-line
>
> Any help apppreciated.
>
> Ed

Steve Berman