From: Robert Klemme <shortcutter@...>
Date: 2010-08-22T18:15:13+09:00
Subject: Re: A small problem for arrays

On 21.08.2010 18:27, Jean-Julien Fleck wrote:
> 2010/8/21 Unc88 Unc88<unc88@mail.ru>:
>> Can do the subtraction of arrays without using the operator "-"?
>> Is there a standard method in the class Array?
>
> "-" *is* a standard method of class Array. The apparent "operator"
> behavior is just syntaxic sugar added on it:
>
>>> a1 = (1..10).to_a
> =>  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> a2 = (5..7).to_a
> =>  [5, 6, 7]
>>> a1.-(a2)
> =>  [1, 2, 3, 4, 8, 9, 10]
>
> Last line call "-" method of object "a1" with object "a2" as an argument.
>
> ~>  ri Array.-
>
> ---------------------------------------------------------------- Array#-
>       array - other_array    ->  an_array
> ------------------------------------------------------------------------
>       Array Difference---Returns a new array that is a copy of the
>       original array, removing any items that also appear in other_array.
>       (If you need set-like behavior, see the library class Set.)
>
>          [ 1, 1, 2, 2, 3, 3, 4, 5 ] - [ 1, 2, 4 ]  #=>   [ 3, 3, 5 ]
>
> Cheers,
>

Just adding to that: if Arrays are large and / or there are frequent set 
operations needed then using class Set might yield better performance.

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/