From: dblack@...
Date: 2003-05-14T03:21:23+09:00
Subject: Re: Regexp: why does (re)* return only last repetition?

Hi --

On Wed, 14 May 2003, Austin Ziegler wrote:

> Okay, I think the problem here is:
>
>   a = "[a-z\\]"
>   b = /#{a}/
>
> When the RE is being built, a is being interpolated again. If I've
> built my regular expression source string properly, it should NOT be
> interpolated again. Is there any way to build a RE from a string
> which does not reinterpolate the string? Is there a way to add such
> a functionality if it does not exist?

I'm not sure what you mean by "interpolate again" (or reinterpolate).
I think everything is happening just once: you've created a string
([a-z\]), and you're interpolating it into a regex.

> Frankly, /#{a}/ for the above string should be no different than
> /[a-z\\]/.

Except... a is a 6-char string ([a-z\]), and the contents of the regex
there is 7 characters :-)  There's no way for Ruby to backtrack and
know that, when you created the string, you typed \ twice.  You might
have produced the string this way:

  a = [91, 97, 45, 122, 92, 93].map {|c| c.chr}.join   # [a-z\]


David

-- 
David Alan Black
home: dblack@superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav