Re: looking-back

* Andreas Röhler <[email protected]> [2026-08-01 15:56]:
> Hi,
> 
> 
> want to match an opening paren followed by a whitespace. Tried the forms
> below without success.
> Any suggestion?
> 
> ( (looking-back "\\\\( +" (line-beginning-position) t)  ==> nil
> ( (looking-back (regexp-quote (rx "(" (+ space))) (line-beginning-position)
> t) ==> nil

;; Step 1: Type this literal text on a new line (without quotes or backslash):
( hello)

So you need to place cursor after space like where is "h" in hello and
evaluate: (looking-back "( +" (line-beginning-position) t)

So it gives me true at h. But not if I press cursor at "e" in hello
above.

You probably wanted to lookback longer than that...

( (re-search-backward (rx "(" (+ space)) (line-beginning-position) t) => 706 so this one would put cursor backwords... on the "( "


( (save-excursion (when (re-search-backward "( +" (line-beginning-position) t) (match-string 0))) ⇒ #("( " 0 2 (face font-lock-string-face fontified t))

(save-excursion (when (re-search-backward "( +" (line-beginning-position) t) (substring-no-properties (match-string 0)))) ⇒ "( "

(save-excursion (when (re-search-backward "( +" (line-beginning-position) t) (list (match-string-no-properties 0) (match-beginning 0) (match-end 0)))) ⇒ ("( " 1166 1168)

means finding this one                    ^^^^^


(save-excursion
  (when (re-search-backward "( +" nil t)  ; nil = no limit
    (list (match-string-no-properties 0)
          (match-beginning 0)
          (match-end 0)))) ⇒ ("( " 1389 1391)


-- 
Jean Louis