From: Mark Wilson <mwilson13@...>
Date: 2003-10-02T03:34:43+09:00
Subject: Re: Making == symmetric?


On Wednesday, October 1, 2003, at 02:16 PM, Marcin 'Qrczak' Kowalczyk 
wrote:

[snip]

> This is like saying "my programming model is unable to describe the
> reality accurately, so let's change the reality to make it fit the
> model".
>
> For me this is simply a shortcoming in the traditional 
> single-dispatched
> OO way of thinking, that it can't make the meaning of == depend on the
> types of both arguments.
>
> I don't say that the language should enforce == to be symmetric. I say
> that the language should allow to define a symmetric == with the 
> desired
> meaning.
>
> [snip]

I think Ruby does allow one to define a symmetric ==. As a general 
matter, I think a language is only required to enforce a symmetric == 
for objects of the same class (or values of the same type) in order to 
have algebraic closure.

Regards,

Mark