From: dblack@...
Date: 2006-07-26T23:57:32+09:00
Subject: Re: I'll have the duck!

Hi --

On Wed, 26 Jul 2006, Dumaiu wrote:

> ara.t.howard@noaa.gov wrote:
>>
>> i was thinking about this on my ride home and recalled a term used in damian
>> conway's object oriented perl book (a fastastic book on oo programming btw.)
>> and a term he used way back then : 'interface polymorphism.'  the more i
>> thought about it the more i like the term better than 'duck typing' because
>> it's closer in spirit to the idea of something being an acceptable object
>> merely by implimenting (via method_missing or whatever) a certain set of
>> behvaiours.
>>
>
> 	Holy cow; the whole thread was worth it just for this.  This is on
> target: in ruby-talk 03608 matz in fact mentions as an illustration of
> 'implementation polymorphism' the Enumerable module, because the use of
> each() is the only requirement defined for compatibility.  I will posit
> as a distinction that 'duck typing,' as we call it, is a description of
> an innate behavior of the language, while 'implementation inheritance'

(Do you mean 'interface polymorphism'?)

> would be D. Conway's name for the general consequence of building
> projects with this kind of model in mind.

Don't forget, though, that duck typing was originally intended as a
description of something that a programmer does.  I've also always
tended to see it as a property of the language (i.e., Ruby as a
"duck-typed" language, as Jim Weirich has said) -- since the
method-call is always isolated from any ancestry checks and so forth
that surround it -- but, as I understand Dave's take on it, it does
refer at least equally to a programming attitude/style/philosophy (or
whatever the best term is).


David

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