> Lett Jeff Davis <jdavis-list / empires.org>
> Aihe: regex questions
> 
> In python the regexes allow you to call a function instead of just 
> substitute the values (see <http://docs.python.org/lib/node111.html> for 
> more details). That seems quite useful, is there something similar in ruby?
> 
> Also, let's say I want match anything between "a" and "b" unless it 
> contains the word "foo". I could write two regexes like so:
> 
> if str =~ /a(.*)b/ and str !~ /a(.*foo.*)b/
> 
> Is there a good way to make that kind of logic into one regex? Is there 
> some kind of "intersect" operator or a "not" operator?

There's /(?!foo)/x, but I can't think of any proper way to get it to 
accept all other strings but the one specified. You could just invert your problem and reject any strings that *do* have a 'foo' between.

unless str =~ /a.*?foo.*?b/

If you need to, you can group to extract the non-foo part there.

> Regards,
>     Jeff Davis

E