From: "David A. Black" <dblack@...>
Date: 2005-11-25T22:23:03+09:00
Subject: Re: Faster way to pick the every other array member?

Hi --

On Fri, 25 Nov 2005, Damphyr wrote:

> we have [1,2,3,4,5,6,7] and want [2,4,6]
>
> Is there a way other than
>
> fields=[1,2,3,4,5,6,7]
> fields.collect!{|f|
> 	f if fields.index(f)%2==1
> }.compact!
>
> And by another way I mean something shorter and more beautiful :).

Here's one possibility:

irb(main):016:0> a = [1,2,3,4,5,6,7]
=> [1, 2, 3, 4, 5, 6, 7]
irb(main):017:0> res = []
=> []
irb(main):018:0> (1...a.size).step(2) {|n| res << a[n] }
=> 1...7
irb(main):019:0> res
=> [2, 4, 6]


David

-- 
David A. Black
dblack@wobblini.net