From: Robert Klemme <shortcutter@...>
Date: 2008-03-27T03:34:55+09:00
Subject: Re: The inject function

On 26.03.2008 15:32, Eustáquio 'TaQ' Rangel wrote:
> You could use a test to sum the number only when it's even on inject, but
> 
> [1,2,3,4,5,6].inject {|m,v| m + (v%2==0?v:0) }
> 
> results to 13, because seems that the value of m is automatically the first
> element of the array. On this case, you can tell it to start with 0:
> 
> [1,2,3,4,5,6].inject(0) {|m,v| m + (v%2==0?v:0) }

Actually these two are not equivalent!  You should usually use the 
second form because the first form will return nil for an empty Array.

Btw, Radoslav's solution omits unnecessary additions of 0:

[1,2,3,4,5,6].inject(0) {|m,v| v % 2 == 0 ? m : m+v }

> | Second, I need to reverse an array using only the inject command. So,
> | something like above with the result [4,3,2,1]
> 
> Why don't you use reverse?

I assume it is some kind of task assignment - which is why I regret that 
solutions were posted so quickly.

Kind regards

	robert