From: Eli Green <eli.green@...>
Date: 2001-08-08T13:07:08+09:00
Subject: [ruby-talk:19330] Re: Perl/Python/Ruby common backend (Parrot, can Ruby play too?)

from Alex Martelli on 2001-08-08 at 01:46:11:
> "Tom Robinson" <tom@alkali.spamfree.org> wrote in message
> news:8afvmt8ck86d7ug5clnu3h0qek4hb7ope0@4ax.com...
>     ...
> > >> need that might be unique to Ruby?  [One that comes to mind: the
> ability
> > >> to extend an existing class.]  For the
> > >
> > >In what sense is this "unique to Ruby"?  The following works in Python:
>     ...
> > He might be talking about the way you can reopen and extend existing
> > _built_in_ classes in Ruby, for example:
> 
> Ah, I see -- Python's classes aren't divided between builtin and
> not-builtin (they all work the same way), but there's a distinction
> between classes and *types* (which is slowly and gradually being
> removed) -- types cannot be manipulated as freely as classes.

There's no distinction in ruby between classes that are builtin or not, as far
as I can tell. I think what he was referring to was Python's types (that are a
little too static for most rubyers tastes).

However, since the Python community has been leaning towards that pure-OO
re-write (affectionately referred to as Python 3000), I would not be surprised
if Parrot were the catalyst to said re-write.

In any case, it seems like the capability will most assuredly be there in the
Parrot VM. Especially since I'm sure some ruby-internals-guru will be prodding
them the whole time. =)

> > class Regexp
> >   alias oldcomp =~
> >   def =~ (astring)
> >      match(astring)[1..9]
> >   end
> > end
> >
> > ...Regexp being part of the standard library.  Can you do this in
> > Python?  It would be nice...
> 
> Python's re module offers factories for re-object that are
> instance of types, not of classes -- therefore, in Python's
> current version, no such manipulation is possible.  The
> current Pythonic solution is to wrap type instances into
> class instances (see my recipe
> http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52295
> to see how auto-delegation replaces inheritance for this
> kind of purposes), whereupon all manipulation becomes
> possible (and easy).  Of course, the module itself would
> be replaced with one that wraps it and supplies factory
> functions returning the wrapped-objects directly (using
> techniques close to the one I show in my popular recipe
> http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/65207).
> 
> But this doesn't retroactively affect type-instances that
> were created *before* the wrapping, so it's not fully
> equivalent to what one can do starting in Python 2.2
> (which introduces type->class inheritance and a few other
> such enhancements -- definitely a start on the road of
> type/class equivalence).  In particular, such polymorphic
> 'tricks', just like about any kind of polymorphism, are
> defeated by the accursed practice of type-testing (I
> recommend some alternatives in my recipe
> http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52291).
> 
> 
> Alex