From: mike leonard <mikeleonard@...>
Date: 2008-03-22T00:19:58+09:00
Subject: Re: A question involving variable evaluation

On Mar 21, 7:57 am, mike leonard <mikeleon...@gmail.com> wrote:
> Hello friends,
>
> I'm working on some code that will iterate through an array of regex
> patterns and values, returning a value when the corresponding regex is
> matched:
>
> the_string = "foobar"
> patterns_and_values = [[/(foo)(.*)/, "bar"], [/(bar)/, "foo"]]
> patterns_and_values.each do |p|
>     the_match = the_string.match(p[0])
>     if the_match then
>         return p[1]
>     end
> end
>
> To make this more useful, I'd like to be able to use the subexpression
> globals in the value that is returned, like so:
>
> patterns = [[/(foo)(.*)/, $~[0]], [/(bar)/, $~[1]]
>
> However, what is actually returned is the value of $~[0] at the time
> that the patterns array was created, which is nil. Is there a good way
> to achieve this without resorting to eval? I'd like to keep the syntax
> of the patterns_and_values array as simple as possible, since this
> will be exposed to users so that they can add to it as necessary.
>
> Thank you kindly in advance (and apologies if the above syntax isn't
> quite right - I don't have Ruby installed on this machine).
>
> --Mike Leonard

To simplify this somewhat convoluted question:

After I assign the pattern matching globals ($~[0] et al) to a
variable, is there a way to re-evaluate this variable after a match
has occurred, so as to keep it consistent with the actual current
value of $~[0], as opposed to what the value was when the variable was
created?

Many thanks,

Mike Leonard