From: Daniel Berger <djberge@...>
Date: 2003-04-08T22:54:25+09:00
Subject: Re: Array Sutraction

Jim Freeze wrote:
> 
> Ok, this has been discussed at length previously,
> and it appears that the implementation has
> changed.
> 
> Consider:
> 
>   # in 1.6.7
>   [1,1,2,2,3,3] - [3] => [1,2]
> 
>   # in 1.8.0
>   [1,1,2,2,3,3] - [3] => [1,1,2,2]
> 
> I think this last algorithm was chosen for
> performance reasons. The problem is, the #- operation
> is neither explainable by the Array being considered a bag
> or a set. Plus, since this operation seems to change
> with revisions, it is hard to rely upon.
<snip>

FWIW, 1.8 has a Set class if you want true set behavior:

require "set"
set_a = Set.new([1,1,2,2,3,3])
p set_a -> #<Set: {1, 2, 3}>

set_b = set_a -[3]
p set_b -> #<Set: {1, 2}>

Regards,

Dan

-- 
a = [74, 117, 115, 116, 32, 65, 110, 111, 116, 104, 101, 114, 32, 82]
a.push(117,98, 121, 32, 72, 97, 99, 107, 101, 114)
puts a.pack("C*")