Subject: bug#47534: Subject: 28.0.50; Regexp lower case pattern matches upper case

From: "Basil L. Contovounesios" <[email-masked]>
Date: Wed, 31 Mar 2021 23:25:05 +0100

dalanicolai <[email-masked]> writes:

> When using the regexp builder and trying to match only lower case
> letters (and spaces), Emacs also includes upper case matches.

I think this is the effect of the user option case-fold-search, which
defaults to non-nil (this is the case across most search-related parts
of Emacs, including Isearch).  You can toggle it in re-builder
specifically with C-c C-c (reb-toggle-case), or across all buffers by
customising case-fold-search to be nil.

> Also, I am unable to find in the manual any information about the
> option of setting different syntaxes in the regexp builder

I think most of the documentation for re-builder.el is in its commentary
at the start of the file; see M-x find-library RET re-builder RET.

I haven't used re-builder much, but from M-x customize-group RET
re-builder RET I see there is a user option reb-re-syntax for
controlling the default syntax.  C-h m in the re-builder buffer further
reveals that the command C-c C-i (reb-change-syntax) can modify
reb-re-syntax on the fly.

> (also the option is not mentioned in the regexp-builder docstring). So
> I would additionally like to report this as a documentation bug.

Are you referring to the docstring of the re-builder command, or
something else?  And is it a listing of key bindings you would like to
see, or something else?  Would you like to provide a patch with
suggestions for improvements?

Thanks,

-- 
Basil