[racket] Backreference question (regex)

From: Carl Eastlund (cce at ccs.neu.edu)
Date: Fri Oct 29 17:33:25 EDT 2010

I'm not sure I know what problem you're running into, but if you use
Perl regular expression be sure to use (pregexp ...) to compile them
or #px"..." to write them.  Otherwise you get a slightly different
regular expression language (compatible with Unix utilities like
egrep, rather than with Perl).  If you're using those regular
expressions, they don't have backreferences.

Carl Eastlund

On Fri, Oct 29, 2010 at 5:29 PM, Justin Phillips
<jjustinphillipss at gmail.com> wrote:
> I'm trying to write a small regex that would return any repeating pattern in
> a string e.g. ("ababcdcdababcdcd" would return "ab" "cd" abab" "cdcd"
> "ababcdcd")
> I'm having trouble using the backreferencing. I see under section 3.7.2 of
> the guide (and also some Perl docs I've checked out) that I should be able
> to write a simple regex "(1)\1" which would return true for the data "113"
> but Racket says I'm wrong. Any help would be greatly appreciated.
> -Justin

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