From: Austin Ziegler <austin@...>
Date: 2003-11-20T06:10:50+09:00
Subject: Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata about attribute types)

On Thu, 20 Nov 2003 04:37:50 +0900, Sean O'Dell wrote:
> On Wednesday 19 November 2003 11:05 am, Yukihiro Matsumoto wrote:
>> A class has interface; a class can be used as interface (by set
>> of its methods); but it should not be checked by kind_of? or
>> anything based on inheritance, just because it hinders
>> flexibility of dynamic typing so much; remember StringIO or
>> tempfile examples.
> But again, that flexibility is LOST when you have to pass an
> object to a method that REQUIRES it to behave a certain way. The
> flexibility is already gone; it wasn't eliminate by a language
> quirk, it was eliminated by the need of the method being called.

This argument is circular.

> I'm only talking about checking that a certain interface is
> present. Just for the purpose of providing an informative error
> message when an object which cannot fulfill the needs of a method
> is passed. Right now, it just explodes with an ugly message about
> something that happened deep in the called method. Something more
> informative would go a LONG way.

Static typing in Ruby carries too high a performance price, because
*everything* (including class and method definitions) are executed
at runtime.

Far better to have an interface publication mechanism than static --
or "strong" typing.

-austin
--
austin ziegler    * austin@halostatue.ca * Toronto, ON, Canada
software designer * pragmatic programmer * 2003.11.19
                                         * 16.05.20