From: Mathieu Bouchard <matju@...>
Date: 2005-03-26T12:02:29+09:00
Subject: Re: Instead of templates


On Thu, 24 Mar 2005, Adelle Hartley wrote:

>   class A << MyBaseClass
>     def self.DoMyThing(klass=self)
>       ...
>     end
>   end
>   class B << MyBaseClass
>     def self.DoMyThing(klass=self)
>       ...
>     end
>   end
>   class C << B
>     def self.DoMyThing(klass=self)
>       ...
>     end
>   end
> If I were writing this in C++, I'd use templates.  What's the Ruby Way?

I don't claim to represent the "Ruby Way", but personally I've done
similar things (in the RubyX11 project) that implement
parametrized-classes this way:

In each parametrized class, make a (class-wide) hash, and then create new
subclasses on-demand, remembering them in that hash. Then I may allow a
syntax like:

  List.of(Float)

or

  List[Float]

... as typenames, which get associated with an anonymous class that
subclasses my baseclass.

e.g.:

class A
  @special={}
  def self.of(t)
    @special[t] ||= Class.new(self) { @mytype=t; ... }
  end
end

Where "..." may be any specialisation-specific code, e.g. an eval that
recreates some methods in a speed-optimised way depending on t.

Does that make sense?

However I have no experience combining regular inheritance and this
technique, and I know this technique may be difficult to combine with
regular inheritance in a way that makes it really closer to C++.

Btw, what's the class A<<MyBaseClass syntax? AFAIK it's either class
A<MyBaseClass or class<<A. Is this a new syntax?

_____________________________________________________________________
Mathieu Bouchard -=- Montr�al QC Canada -=- http://artengine.ca/matju