From: Robert Klemme <bob.news@...>
Date: 2003-04-08T17:33:20+09:00
Subject: Re: Array Sutraction


"Jim Freeze" <jim@freeze.org> schrieb im Newsbeitrag
news:20030408003523.A678@freeze.org...
>  I'm sorry Matz, I don't understand.
>
>  I don't have a horse in either the set or bag race.
>  It's just the current implementation is very confusing.
>
>  If I have a = [1,1,2,2,2] and I subtract [2], then
>  I should get [1,1,2,2] if a is considered a bag.
>  If a is considered a set, then it must first be
>  temporarily converted to a set [1,2] and then
>  the subtraction is performed yielding [1].

I don't find this confusing. In fact I find the implicit application of
uniq (older version) more confusing because it is somewhat surprising - at
least to me.  In that case substraction indeed combines two operations.

I'd view the substraction "a-b" as "remove all elements in b from a",
which would reasonable lead to all 2's removed from [1,1,2,2,2] yielding
[1,1].

>  However, 1.8.0 returns [1,1].
>
>  ruby -ve 'p [1,1,2,2,2]-[2]'
>  ruby 1.8.0 (2003-03-10) [i386-freebsd4.6]
>  [1, 1]

That's what I'd expect.

    robert