From: transfire@...
Date: 2006-07-25T02:49:28+09:00
Subject: Re: I'll have the duck!


Daniel DeLorme wrote:
> benjohn@fysh.org wrote:
> > I also like it because I don't think that there's anything especially
> > fundamental about classes. With predicate classes, all you're really
> > saying is that "if I've got something that can do x and y, then I know
> > that I can equally validly think of it as something that can do z".
>
> The concept really piqued my interest, and since ruby gives us such nice
> metaprogramming abilities, why not do it?
>
> module DuckTyping
>    @@quacks = Hash.new{ |h,k| h[k] = {} }

[snip cool code]

> ducktype :quack do
>    def quack_loudly
>      quack.upcase
>    end
> end
>
>
> class Duck
>    def quack
>      "quack!"
>    end
> end
>
> class Dog
>    def bark
>      "woof!"
>    end
> end
>
> Duck.new.quack_loudly #=> "QUACK!"
> Dog.new.quack_loudly  #=> NoMethodError
>
>
> nifty?

Nicely done! Code worthy of experimentation. A lot of excellent
comments in this thread too.

I wonder then, if we take up John Carter's notion on duck as mixin,
then Enumerable can be defined as:

  ducktype :each do
    def collect
      each{ |e| yield(e) }
    end
    ...
  end

Although clearly the distinction between a mixin and a ducktype is the
ducktypes global influence. Quite powerful! Yet, I do imagine that with
this is place someone would call for selector namepsaces to reign in
the abundant flocks ;) Onefurther step would have to be taken, at the
very least. a means of constraining them to specific scopes. Perhaps
that's a simple as limiting them the module space they are defined in?

In any case very interesting. I really wonder just how far one can take
this shift in paradigm?

T.