From: Alex Martelli <aleaxit@...>
Date: 2003-09-15T00:43:56+09:00
Subject: Re: Duck Typing

Luc Heinrich wrote:

> Mark Wilson <mwilson13@cox.net> wrote:
> 
>> I've seen some adoption of the term among python people recently.
> 
> What ? They stole that too ?? :>

I would claim independent invention, given that my post of Jul 2000
to c.l.py where I mused:
"""
In other words, don't check whether it IS-a duck: check
whether it QUACKS-like-a duck, WALKS-like-a duck,
etc, etc, depending on exactly what subset of duck-like
behaviour you need to play your language-games with.  If
the argument fails this specific-ducklyhood-subset-test, then
you can shrug, ask "why a duck?" (at least, you can if you're
a Marx Brothers fan and have memorized "Cocoanuts"' script;
Monty Python one-true-wayists will have to find their own
simile here), and move on to the next set of tests (why-a-no-
chicken immediately comes to mind, but then one would have
to ask why it crosses the road, so I think we'd better snip it).
"""

was done before I had ever heard of Ruby, and explained as
"""
My instinctive approach (and it may be that I still haven't
developed the "right" Python instincts, because I haven't 
been using it long!)
"""

while the first mention I can find in comp.lang.ruby is in
a Jan 2001 post by Ben Tilly:
"""
Imagine a language where you are constantly telling the
language everywhere that you have a duck because it is
walking like a duck and talking like a duck.  This is
built into everything that you do.  Then suddenly you
find out that it isn't really a duck after all.
"""

Of course, it's quite possible that Google Groups' archive
is incomplete for either or both languages.


Alex