From: Orion Hunter <orion2480@...>
Date: 2003-06-10T03:43:42+09:00
Subject: array.uniq does not use == ?

I have a user defined object, Agent.  And I want to pass my Agents around in 
an Array.  I've "mixed-in" the  Comparable module, and defined <=> within 
the class for sorting purposes.   However, I _also_ want to be able to 
perform Array.uniq/Array.uniq! as well, having the decision on the 
"uniqueness" of the object derived from one particular attribute.

My first thought was that all I need to do was define == in my Agent, and I 
had hoped/assumed that this was the operator/function that Array.uniq looked 
at when it executed.  However, this is not the case.  My next thought was 
that Array.uniq might use <=>, and consider them "equal" if this returned 0, 
however this was not the case either.

I have tried defining the following for my object:

<=>
==
===
eql?
equal?

but none of them seem to be used in the Array.uniq comparison.  Further 
investigation showed that a combination of overriding eql?() and hash() will 
do the trick (are these _both_ used in uniq?).  Now, I know that I can 
create my own class which inherits from Array, and override the uniq and 
uniq! funciton to do what I want, but it seems like there is a less clumsly 
solution (it just seems like I shouldn't have to override hash()).  Any 
suggestions?  Thanks.

Matt

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