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Why looking-at-p works?


From: Marcin Borkowski
Subject: Why looking-at-p works?
Date: Tue, 06 Mar 2018 08:57:42 +0100
User-agent: mu4e 1.1.0; emacs 27.0.50

Hi all,

(defsubst looking-at-p (regexp)
  "\
Same as `looking-at' except this function does not change the match data."
  (let ((inhibit-changing-match-data t))
    (looking-at regexp)))

What happens is that if I make looking-at in the above code fail (e.g.,
by saying (looking-at-p 123)), inhibit-changing-match-data remains nil,
even though there is no unwind-protect here.  Why does it work like
this?

TIA,

-- 
Marcin Borkowski
http://mbork.pl



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