Compare regular expressions

[Diez B. Roggisch]

Adam Atlas schrieb:
> On Apr 16, 1:50 pm, "Diez B. Roggisch" <d... at nospam.web.de> wrote:
>> It's not. For the simplest of expressions one might come up with a
>> relation between them, but even that would be hard. General case? No chance.
> 
> I wouldn't say there's 'no chance'. It would require external parsing,
> for sure, but if anything, it may only be impossible for unusual
> cases.

The external parsing of regular expressions is cheap. But once you are 
there, how do you proceed? That's where it becomes hard. I can think of 
some simple strategies, but nothing that can't be easily found a 
counter-example for.

Diez