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Re: Macro aborts even though regexp instance exists - Serious Bug

From: David Combs
Subject: Re: Macro aborts even though regexp instance exists - Serious Bug
Date: Fri, 30 Nov 2012 21:57:50 +0000 (UTC)

In article <>,
Kevin Rodgers  <> wrote:
>On 10/22/12 2:40 PM, Swami Tota Ram Shankar wrote:
>> Hi emacs users,
>> I write a simple macro which works, however, it fails in a particular
>> case.
>> C-s
>> M-r
>> to get into isearch-forward-regexp
>> and give a regexp like
>> It works for every TWO and ONE as long as there is a ONE ahead of TWO.
>> In the last instance, no ONE exists after TWO and it fails.
>> \|<=>  OR or disjunction.
>> Any solutions?
>> This is such a fundamental issue that I think its a bug. When the C-s
>> M-r  is used outside the macro definition, the cursor gladly returns
>> to the original position when OR is entered and proceeds forward from
>> there, but perhaps, the macro aborts.
>It is not a bug: when ONE fails to match the buffer, C-s (which is designed
>for interactive use, obviously) signals an error, which terminates the macro
>That's because there is no way for C-s to know that you _might_ type \|TWO
>after ONE.
>So the solution is to make sure that the regexp is not complete after ONE:
>C-s \(ONE\|TWO\)
>> I guess, this can lead to a lot of confusion and time wastage, if the
>> user is unaware of this and most likely to neglect it because its
>> contrary to normal usage.
>Yes, there is a lot of confusion and wasted time when a user is not aware
>of how to use a program.
>> I include more newsgroups because of the seriousness of this bug.
>Whatever :-)
>Kevin Rodgers
>Denver, Colorado, USA


(2) "when a user is not aware of how to use a program": I don't know
    that this thread really falls under that.  Although your solution
    and especially the reason for it "obvious" -- but only once you've
    seen it.  It's actually a little subtle.

    AND I believe it's so important (and easy to get wrong) that
    it should be added to the emacs manual (in macros) AND to
    any much-used cheat-sheets -- plus the wiki, of course.

    Perhaps you (as one of the real gurus around here) could write
    a paragraph and example and ask the developers to put it into
    the right places.

Thanks again for the pointer!


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