From: Tim Pease <tim.pease@...>
Date: 2007-02-15T03:33:23+09:00
Subject: Re: Programmatically turning a Regexp into an anchored Regexp

On 2/14/07, Greg Hurrell <greg.hurrell@gmail.com> wrote:
> Is there any programmatic way to take a Regexp like /foo/ and turn it
> into an anchored Regexp (/^foo/)? I'm looking for a programmatic way
> to do this because the actual Regexp is dynamic, not known until run
> time.
>
> I'm wishing for an option or method similar to the EXTENDED,
> IGNORECASE, MULTILINE options, except for anchoring.
>
> I suspect the answer will be "no", but I wanted to ask anyway before
> giving up hope...


def anchor( rgxp )
  Regexp.new "^#{rgxp.inspect[1...-1]}"
end

I would recommend using the '\A' anchor instead of the '^' anchor.
'^' matches at the beginning of a line so that "blah blah\nfoo" would
match. '\A' matches at the beginning of the string so that "blah
blah\nfoo" will not match, but "foo\nblah blah" will match.

def anchor( rgxp )
  Regexp.new "\\A#{rgxp.inspect[1...-1]}"
end


Blessings,
TwP