From: Logan Capaldo <logancapaldo@...>
Date: 2006-07-13T02:21:30+09:00
Subject: Re: Help with a regexp


On Jul 12, 2006, at 10:10 AM, Daniel Schierbeck wrote:

> I'm trying to write a regular expression that matches bencoded  
> strings, i.e. strings on the form x:y, where x is the numeric  
> length of y.
>
> This is valid:
>
>   6:foobar
>
> while this is not:
>
>   4:foo
>
> I've tried using #{$1} inside the regexp, but it seems $1 is still  
> nil at that point. Here's what I've got so far:
>
>   /^([1-9]+\d*):(\w){#{$1}}$/
>
> (it ain't working)
>
> I'm matching with `string =~ regexp'; would it be better if I did  
> it another way?
>
>
> Cheers,
> Daniel
>

I believe that this is not in the set of languages a Regexp can  
match. As others have already suggested you'll have to do it in 2 steps.