From: "Hal E. Fulton" <hal9000@...>
Date: 2003-08-08T08:14:40+09:00
Subject: Re: Ducktype, right?

----- Original Message ----- 
From: <dblack@superlink.net>
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Sent: Thursday, August 07, 2003 5:41 PM
Subject: Re: Ducktype, right?


> I would describe "duck typing" not as a particular programming
> technique, but as a way of understanding how Ruby objects present
> themselves with regard to the notion of type.  Any Ruby object has
> the potential to be customized, so to speak, as to its behavior and
> interface.  So there's a kind of circularity, when it comes to
> describing the type of an object: an object is of type
> "the type which is the type of objects that behaves the way this object
> behaves".  Hence (as I understand it) the idea of "duck typing": if it
> behaves (walks, quacks, etc.) like a duck, then it's a duck.

Thanks for saying this so well, David. I was trying to 
collect my thoughts, but I think you just collected them. :)

> > This is sort of like having a discovered mixin.  Neat.
>                               ^^^^^^^^^^^^^^^^^^
> 
> Intriguing phrase.  What do you mean exactly? :-)

Yeah, I wondered that, too. Original poster: Please elaborate...

<offtopic>
When I was working on _The Ruby Way_ and gathering quotations
to intersperse in the material -- and I admit some of these
are kind of hokey -- I was thumbing through the writings of
Confucius. No, seriously. And I found a quote that I almost
used, that reminded me of duck typing: "If an urn does not
have the properties of an urn, can it truly be said to be
an urn?" :) That may be wrong, it's from memory. Intriguing,
though, isn't it? Predates Bishop Berkely, John Locke, 
Immanuel Kant by 2000 years. Perhaps even predates Plato. 
My history isn't that good.
</offtopic>

Hal

--
Hal Fulton
hal9000@hypermetrics.com