5 minutes ago, Mark Engelberg wrote:
> As far as I can tell, pregexp functionality is a superset of regexp
> functionality. Furthermore, the added functionality uses patterns
> that are unlikely to occur by accident in normal regular
> expressions. So is there any advantage to using regexp over
> pregexp?
No, they're just two slightly different pattern languages.
> Why is there a need for both to coexist in Racket? What would be
> the downside to removing regexps from the language?
Originally, there was concern over existing patterns that would break
in hard-to-find ways. I guess that removing `regexp' and the `#rx'
syntax could be used as a brute-force way that makes everyone upgrade
code immediately, but such breakages tend to leave behind useful code
with inactive maintainers.
But I see another advantage for that now -- similar to having all
three `fgrep', `grep', and `egrep' programs on a linux box. It's just
easy to use the language that fits you more.
In that spirit, I won't even mind some
#lx"foo" -- literal regexp, same as (regexp (regexp-quote "foo"))
possibly even
#gx"foo" -- globbing regexp, where you only have "*", "?", and
"[...]".
but this one can get tricky, since it has many incompatible variants
(eg, linux shells don't match a "." in the beginning unless it's
explicitly in the pattern, and usually "*" doesn't match "/").
--
((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://barzilay.org/ Maze is Life!
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