From: dblack@...
Date: 2006-09-28T08:33:03+09:00
Subject: Re: Injecting truth

Hi --

On Thu, 28 Sep 2006, Ken Kunz wrote:

> I had a scenario arise today where I needed an iterator with similar
> semantics as Enumerable#all?, but non-short-circuiting. We came up with
> a fairly elegant solution (imho), so I thought I'd be a good rubyzen
> and share :)
>
> 1) First... the standard #all? (short-circuits):
>
> irb> (1..5).all? { |i| puts i; i < 3 }
> 1
> 2
> 3
> => false
>
> 2) Non-short-circuiting version (injecting truth):
>
> irb> (1..5).inject(true) { |retval, i| puts i; retval &&= (i < 3) }
> 1
> 2
> 3
> 4
> 5
> => false
>
> 3) One more way (though I like #2 better)
>
> irb(main):016:0> (1..5).partition { |i| puts i; i < 3 }.last.empty?
> 1
> 2
> 3
> 4
> 5
> => false

Cool.  I want to play too :-)

>> [*1..5].map {|i| puts i; i < 3 }.all?
1
2
3
4
5
=> false


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org