Re: Whitespace search and regex.c

[Juri Linkov]

I have no strong opinion on whether changing regex.c was a good thing
or not (after all, Perl already entered on the same path where its regexp
engine is modified every time someone fells a need to add a new feature.
BTW, setting `search-spaces-regexp' to the empty string would allow
to improve Emacs regexp readability similar to the /x modifier in Perl
regexps.  I won't elaborate on how useful it is, but I always wished
that Emacs regexps would use features of Perl regexps).

Anyhow, I want to note that there is a bug in the current
implementation of `search-spaces-regexp' feature.  The space
at the end of a regexp is interpreted literally, not as a whitespace
specified by `search-spaces-regexp'.  Whereas the space in the
middle or at the beginning of a regexp is interpreted correctly
(i.e. as a special whitespace character).

Test case:

(let ((search-spaces-regexp "\\s-+")) (re-search-forward "a b"))
finds the first line in the test text below (CORRECT).

(let ((search-spaces-regexp "\\s-+")) (re-search-forward "a "))
finds the second line in the test text below (INCORRECT, it should find
the first line).

Test text:
a       b   (has TAB between `a' and `b')
a b         (has SPC between `a' and `b')

-- 
Juri Linkov
http://www.jurta.org/emacs/