From: Robert Dober <robert.dober@...>
Date: 2006-11-20T23:45:12+09:00
Subject: Cannot override #== with mixin, was help with patch to ruby-core

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Hi all

I have sent a little patch, defining HalfOrder, to ruby-core in order to get
some help with a problem I have found. Maybe this was not the best
procedure.
So I'll try here again :(

basically the patch defines a module HalfOrder which defines ">", ">=", "<"
and "==" depending on "<=", well almost because a potential #== in the Mixer
class, as in Set cannot be overwritten. I think this is a shame.
Here goes some code expressed in ruby instead of C

module HalfOrder
### Mixer has to define #<=

...
def == other
   # in case of performance problems you might want to define == yourself
    self <= other && other <= self
end
...
end

class Set
    include HalfOrder
end

Set.new == Set.new # works while it should raise a NoMethodError for a
missing #<=

well *should* as in I would like.

Any ideas? ( Maybe the HalfOrder module should complain or warn when mixed
into a Class already containing a #==; guess I do not know how to do that in
C, yet)

Cheers
Robert
-- 
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore all progress
depends on the unreasonable man.

- George Bernard Shaw

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