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bug#35708: [27.0.50]: thingatpt.el, thing-at-point-looking-at redundant


From: Andreas Röhler
Subject: bug#35708: [27.0.50]: thingatpt.el, thing-at-point-looking-at redundant
Date: Tue, 14 May 2019 12:49:07 +0200
User-agent: Mozilla/5.0 (X11; Linux i686; rv:60.0) Gecko/20100101 Thunderbird/60.6.1


On 14.05.19 12:02, Andreas Röhler wrote:

On 13.05.19 21:25, address@hidden wrote:
Andreas Röhler <address@hidden> writes:

Thought at something like below, which should pass the test:

(defun ar-thing-at-point-looking-at (regexp)
   "Return t if regexp matches at or before point, nil otherwise."
   (save-excursion
       (while (not (or (looking-at regexp)(bolp)))
       (forward-char -1))
       (looking-at regexp)))
I think it's an optimization to use re-search-backward instead of moving
on character at a time and calling looking-at in lisp.



Hmm, current thing-at-point-looking-at might be slow with large buffers. The slightly modified test should reveal it:

(ert-deftest thing-at-point-looking-at-2 ()
  (with-temp-buffer
    (insert "1abcd 222abcd")
    (dotimes (_ 99999) (insert " asdf "))
    (goto-char (point-min))
    (let ((m2 (progn (search-forward "2abcd")
                     (match-data))))
      (goto-char (point-min))
      (search-forward "2ab")
      (should (thing-at-point-looking-at "2abcd"))
      (should (equal (match-data) m2)))))

But let me correct the alternative delivered, as it didn't match before point:

(defun ar-regexp-atpt (regexp)

"Return t if REGEXP matches at or before point, nil otherwise.

Changes match-data"
  (save-excursion
    (if (looking-at regexp)
    (while
        (save-excursion
          (and (not (bobp))
           (progn (backward-char) (looking-at regexp)))))
      (while (not (or (bobp) (backward-char) (looking-at regexp))))
      (ar-regexp-atpt regexp))
    (looking-at regexp)))





Another fix, as a bug showed up when testing (ar-regexp-atpt "[a-z]+"):

(defun ar-regexp-atpt (regexp)
  "Return t if REGEXP matches at or before point, nil otherwise.

Changes match-data"
  (save-excursion
    (if (looking-at regexp)
    (while
        (and (not (bobp))
         (or (progn (backward-char) (looking-at regexp))
             (forward-char 1))))
      (while (not (or (bobp) (backward-char) (looking-at regexp))))
      (ar-regexp-atpt regexp))
    (looking-at regexp)))







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