From: matz@... (Yukihiro Matsumoto)
Date: 2001-07-13T18:11:14+09:00
Subject: [ruby-talk:17779] Re: What is Array#- ?

Hi,

In message "[ruby-talk:17775] Re: What is Array#- ?"
    on 01/07/13, Stephan K�mper <Stephan.Kaemper@Schleswig-Holstein.de> writes:

|The point here is that Array#- works as if the Array were a set - and
|consquently treats it appropriately by removing duplicates.

Both behaviors are rational, I think.  Last time I made decision, I
took performance.  Set behavoir can be (and is) implemented
efficiently by using hash.  OTOH bag behavior was slow.

There's no reason to make "-" to remove duplication (other than
performance), so that if someone persuade me, it might be change in
the future.  In that case, it would be useful to define new operation
for set subtraction, maybe.

							matz.