From: Austin Ziegler <austin@...>
Date: 2003-04-09T00:52:55+09:00
Subject: Re: Array Sutraction

On Tue, 8 Apr 2003 23:33:17 +0900, Jim Freeze wrote:
> On Tuesday, 8 April 2003 at 22:59:50 +0900, Michael Campbell wrote:
>>> 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].
>> So [1, 1, 2, 2] - [2] should yield the same as
>> [1, 1, 2, 2] - [2, 2]?
>> That seems odd to me.
> Yes. It's not really subtraction as implied by the '-' minus
> operator. Maybe it should be renamed to #remove_all_from. :)

I think it's more confusing when dealing with numbers than with
Objects.

  i = Object.new    # => #<Object:0x277c230> 
  j = Object.new    # => #<Object:0x276fdf8> 
  k = Object.new    # => #<Object:0x2768898> 
  a = [i, j, k, i, i]

  a - [i]           # => [j, k]
  [i].each { |e| a.delete(e) }
                    # => [j, k]

You're removing a specific Object from an array. At least, IMO.

-austin
-- Austin Ziegler, austin@halostatue.ca on 2003.04.08 at 11:48