From: Martin DeMello <martindemello@...>
Date: 2003-09-14T18:23:05+09:00
Subject: Re: Duck Typing

Ryan Pavlik <rpav@mephle.com> wrote:
> On Sun, 14 Sep 2003 15:22:37 +0900
> Martin DeMello <martindemello@yahoo.com> wrote:
> 
> <snip>
>> Any yes, it's by no means specific to Ruby, but it is the way the
>> language defines a 'type'.
> 
> No, it's how _you the programmer_ define a 'type'.  You have a few
> options here; "duck typing" is just one of them.  It has nothing to do
> with what the languages specifies in this case.

The only type checking the language does by default is to (dynamically)
see if a given object responds to a given message. Checking explicitly
for responds_to?, is_a? etc. merely add additional restrictions atop
the type system. By analogy, you could hack the built-in classes so that
all numbers were strictly integral, but you couldn't say that the
language was agnostic towards supporting reals.

martin