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bug#41006: 26.3; regular expressions documentation
From: |
jan |
Subject: |
bug#41006: 26.3; regular expressions documentation |
Date: |
Tue, 5 May 2020 11:05:25 +0100 |
Hi all,
I know this was addressed at Stephan but I'm getting increasingly
puzzled by the difference between what other people are describing and
what I'm seeing.
In the other e-mail Mr Stallman said he could see this:
* Regexp Special:: Special characters in regular expressions.
* Char Classes:: Character classes used in regular expressions.
* Regexp Backslash:: Backslash-sequences in regular expressions.
My emacs (Windows, 26.3) shows
* Regexp Search:: Search for match for a regexp.
* Regexps:: Syntax of regular expressions.
* Regexp Backslash:: Regular expression constructs starting with ‘\’.
* Regexp Example:: A complex regular expression explained.
I started up my ubuntu machine and try to look in the manual to see if
it was different from the windows, FYI I got "Info file emacs does not
exist".
OK... it finally twigged. I've just looked elsewhere. From the emacs menu:
'Search Documentation' submenu 'Look Up Subject In Elisp Manual'
Enter:
regexp RET
Click 'Syntax Of Regexps' gets you to:
"34.3.1 Syntax of Regular Expressions" which looks like what Mr
Stallman has been describing
and finally I can see what Eli has described:
"
‘\{M,N\}’
is a more general postfix operator that specifies repetition with a
minimum of M repeats and a maximum of N repeats. If M is omitted,
the minimum is 0; if N is omitted, there is no maximum. For both
forms, M and N, if specified, may be no larger than 2**15 - 1 .
For example, ‘c[ad]\{1,2\}r’ matches the strings ‘car’, ‘cdr’,
‘caar’, ‘cadr’, ‘cdar’, and ‘cddr’, and nothing else.
‘\{0,1\}’ or ‘\{,1\}’ is equivalent to ‘?’.
‘\{0,\}’ or ‘\{,\}’ is equivalent to ‘*’.
‘\{1,\}’ is equivalent to ‘+’.
"
Now compare this to what's in the user manual (not the Elisp manual):
"
‘\{N,M\}’
is a postfix operator specifying between N and M repetitions—that
is, the preceding regular expression must match at least N times,
but no more than M times. If M is omitted, then there is no upper
limit, but the preceding regular expression must match at least N
times.
‘\{0,1\}’ is equivalent to ‘?’.
‘\{0,\}’ is equivalent to ‘*’.
‘\{1,\}’ is equivalent to ‘+’.
"
The user manual doesn't state that the {,x} syntax is valid where the
Elisp manual does.
thanks
jan
On 05/05/2020, Richard Stallman <rms@gnu.org> wrote:
> [[[ To any NSA and FBI agents reading my email: please consider ]]]
> [[[ whether defending the US Constitution against all enemies, ]]]
> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
>
> > So I go to the "Regular Expressions" node, looking mostly for how to
> > use them. But I find nothing on that there. I only find a review of
> > what looks like everything I already knew about regular expressions.
>
> What I see in master is this structure.
> Is this different from what you saw?
> Does this structure eliminate the problem you had?
>
>
> @node Regular Expressions
> @section Regular Expressions
> @cindex regular expression
> @cindex regexp
>
> ...
>
> @menu
> * Syntax of Regexps:: Rules for writing regular expressions.
> * Regexp Example:: Illustrates regular expression syntax.
> @ifnottex
> * Rx Notation:: An alternative, structured regexp notation.
> @end ifnottex
> * Regexp Functions:: Functions for operating on regular expressions.
> @end menu
>
> --
> Dr Richard Stallman
> Chief GNUisance of the GNU Project (https://gnu.org)
> Founder, Free Software Foundation (https://fsf.org)
> Internet Hall-of-Famer (https://internethalloffame.org)
>
>
>
- bug#41006: 26.3; regular expressions documentation, jan, 2020/05/01
- bug#41006: 26.3; regular expressions documentation, Richard Stallman, 2020/05/02
- bug#41006: 26.3; regular expressions documentation, Mattias Engdegård, 2020/05/03
- bug#41006: 26.3; regular expressions documentation, jan, 2020/05/03
- bug#41006: 26.3; regular expressions documentation, Drew Adams, 2020/05/03
- bug#41006: 26.3; regular expressions documentation, Stefan Kangas, 2020/05/05
- bug#41006: 26.3; regular expressions documentation, Drew Adams, 2020/05/05
- bug#41006: 26.3; regular expressions documentation, Stefan Kangas, 2020/05/05
- bug#41006: 26.3; regular expressions documentation, Drew Adams, 2020/05/05
- bug#41006: 26.3; regular expressions documentation, Stefan Kangas, 2020/05/05
- bug#41006: 26.3; regular expressions documentation, Drew Adams, 2020/05/05
- bug#41006: 26.3; regular expressions documentation, Richard Stallman, 2020/05/06
- bug#41006: 26.3; regular expressions documentation, Richard Stallman, 2020/05/08
- bug#41006: 26.3; regular expressions documentation, Richard Stallman, 2020/05/06