From: RichardOnRails <RichardDummyMailbox58407@...>
Date: 2011-01-23T11:45:30+09:00
Subject: Re: A tad of meta-programming needed

On Jan 20, 8:19 am, Robert Klemme <shortcut...@googlemail.com> wrote:
> On Mon, Jan 17, 2011 at 9:40 PM, RichardOnRails
>
> <RichardDummyMailbox58...@uscomputergurus.com> wrote:
> > Do you have a working example with symbols you could provide me?  And
> > what version of Ruby ran it?
>
> Basically you need a mapping from symbols to group indexes to make
> named groups work in 1.8.  There are several ways you can do that
>
> 1. manual
>
> names = [:foo, :bar, :baz]
> ..
> md = rx.match str
> puts md[names.index(:foo) + 1]
>
> 2. semi automatic
>
> names = [:foo, :bar, :baz]
>
> def names.get(md, name)
>   md[names.index(:foo) + 1]
> end
> ..
> md = rx.match str
> puts names.get(md, :foo)
>
> 3. or even
>
> class MatchData
>   attr_accessor :names
>
>   def get(name)
>     self[names.index(name) + 1]
>   end
> end
> ..
> md = rx.match str
> md.names = names
> puts md.get(:foo)
>
> Further variants are possible.  But I'd switch to 1.9 soon - because
> it's faster and has a better regexp engine with named captures.
>
> Kind regards
>
> robert
>
> --
> remember.guy do |as, often| as.you_can - without endhttp://blog.rubybestpractices.com/

Hi Robert,

Thanks for your response.  As usual, it seems to me,  your response
was thorough.

> Further variants are possible.  But I'd switch to 1.9 soon - because
> it's faster and has a better regexp engine with named captures.

Another responder pointed out the advantage of upgrading to 1.9,
which I will do in a couple of weeks.

My original wish was to use the values from a regex match ($1, $2 ...)
without explicitly listing those symbols in an expression.  Rather I
wanted to extract the values from them in a loop.  Having done some
Ruby meta-programming in past,  but suffering from an increasingly
poor memory in my dotage,  I jotted down "eval($ + i.to_s)", which
failed.

Su Zhang on this thread corrected my error: "put the & in quotes",
along with alternatives.  Problem solved.

Happily, I received a number of other approaches, which I saved
because I love to employ programmatic ways to avoid repetitive program
code.  And now I have the good fortune of getting a bunch of clever
alternatives from you, which I will store with my other gifts.

Since my original problem has been solved,  I'm going to keep on
pushing my project forward.  But I treasure these gifts and promise to
employ them in my continuation education in art of Ruby programming.

Best wishes,
Richard