[ruby-core:25252] Re: RegOOps: An Object-Oriented Approach to Pattern Matching

Caleb,

> This all reminds me intensely of Eric Mahurin's Grammar library/DSL. Much of
> what you're talking about is in there. Any ruby-based parser system (eg
> treetop or racc) is likely to have at least some similarity to this too.
>
> http://rubyforge.org/projects/grammar/

I was unaware of that project. I shall certainly take a look. :-)

>> I've so far talked in terms of matching against Strings, but the
>> generality of this approach suggests that it could be associated with
>> any enumerator. (I've overloaded String#chars to return Char objects
>> for String). This could allow functional-style matching against data
>> structures.
>
> Ah, now you're really reminding me of my own project, Reg (Ruby Extended
>  Grammar). It has pattern-matching constructs for arrays, hashes, objects.
> With backtracking in arrays, even. A whole DSL for matching patterns in ruby
> object trees. The github project is here:
>
> http://github.com/coatl/reg
>
> but, I see you're already following it. :) (There's also a gem, but its
> really old.)

Heh, I'm following it but haven't actually looked at it yet. :-)
Thanks for the pointer.

> I find this subject deeply fascinating. I think it would be cool if ruby had
> more pattern matching built in, so that for instance, you could specify a
> pattern in a block or method parameter list or the left side of an
> assignment. Using unary star and parens, there's already some capability in
> this direction, but it's fairly limited as a pattern matching language
> compared to what Reg can do.

What are your thoughts on the applicability of these features to the
stdlib? Are they generally useful? Is there a "killer app" that the
core team may take notice of? :-)

My approach was to determine what a minimally useful feature set would
look like, so we'd have a starting point for discussion. Perhaps the
lack of interest in this thread indicates that we've been
unnecessarily abstract. :-/

On another note, regarding the Char class I suggested, I noticed that
the ToDo file in the MRI repository has "objectify characters" as a
suggestion. Is there still any interest in this aspect, at least?