Re: Fwd: Emacs-like file buffers

[Bruce Korb <bkorb@gnu.org>]

Jason Meade wrote:
> Is there a standard for regular expressions somewhere?

"a standard"?  No.  "are standards"?  Yes.  Many.  Naturally,
that is the problem.

> It seems like
> most implements (from grep through tcl, perl, and beyond) seem to
> agree on simple stuff like ^[a-c]?002*[^b]+$ etc... (not all
> understand ? and + I've noticed....) but very few seem to share an
> affinity for \w or \< ... \> etcetera.
> 
> I don't use regular expressions (outside of grep) everyday, but when I
> do use them, it's usually for some serious pattern matching, with
> variable capture (via $1, or \#1 etc). I'm starting to incorporate
> search-forward and search-backwards into my filebuffer lib. For that
> kind of work, even strchr will work (sorta. binary data is a problem).
> However, eventually I'll want to be able to regex my buffers, and once
> I add the guile hooks, it would be nice to share the same regex syntax
> with everyone else. After all, the last thing you want is to load a
> module, only to find that it's not syntax compatible with the rest of
> the language!

The most comprehensible and still useful thing would be to provide
a "regcomp" funtion that had a usable implementation of the REG_BASIC
flag and, perhaps, added such tweaks as REG_PERL et al.  The reason
I said, "usable implementation" is because in my implementation of
regexec(3C), REG_BASIC is not defined so there is no way to tell
the regex compiler that I want a basic re.  SO, into the guile.h
family of headers, add:

   #ifndef REG_BASIC
   #  define GUILE_REG_BASIC   0x10000
   #else
   #  define GUILE_REG_BASIC   REG_BASIC
   #endif

then overload "make-regexp" and "regexp-exec" to cope with this and
"I'd-rather-use-Perl-syntax" flags.  Or even a "I-want-fnmatch-
style-globbing" match flag.  It brings all the pattern matching
stuff together making it findable (very important in a huge interface)
and relatively easy to use (i.e. remember).  :)  That's my nickel.

Cheers - Bruce

P.S. one thing missing from the ice-9 regex functions seems to be a way
to pass such flags through to the implementing libguile functions.
Perhaps I just missed how to do it?

(define (string-match pattern str . args)
   (let ((rx (make-regexp pattern))
         (start (if (pair? args) (car args) 0)))
     (regexp-exec rx str start)))


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