bug#41006: 26.3; regular expressions documentation

[jan]

Hi, 3 issues (nothing major).

1. Suggest emacs' excellent documentation should not distinguish between
Regexps and Regexp Backslash in the manual.
That is, these 2 should be combined:


  * Regexps::                   Syntax of regular expressions.
  * Regexp Backslash::          Regular expression constructs starting with ‘\’.

AFAICS the difference is purely arbitrary.
There have been times I've looked for the syntax for such syntax and
found it only because I knew it was there, but not in the same
section. A beginner might conclude emacs doesn't support them.


2. The documentation for {N, M} repetitions matching is incomplete (has
been a long time). Docs say M may be omitted but from testing I find N
may be omitted also ie \{,M\} is valid, and useful.

eg.

ba\{,2\}d

correctly matches only the top 2 of

bad
baad
baaad
baaaad


3. This from the docs

‘\=’
     matches the empty string, but only at point.

baffles me. I've had a hard look for any examples of how it may be used
and found nothing. I feel I may be missing something extremely useful, I
just don't know what!

thanks

jan



In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29 built on CIRROCUMULUS
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor 'Microsoft Corp.', version 6.1.7601
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