From: Stefano Crocco <stefano.crocco@...>
Date: 2011-11-16T06:16:20+09:00
Subject: Re: Logical operator ||

On Wednesday 16 November 2011 06:09:57 Damián M. González wrote:
> Ey guys. Look at this:
> 
>  a = "mom"
>  if a == ( "dad" || "mom" )
>  puts "Hi"
>  end
> 
>  Very simple. I saw a kind of this exercise in a book that I'm studing(
> yes...I'm noob in this ), and I gave it by understood, but now when I'm
> practicing i see that...this has not happen. That chunk of code return
> me nil...but, judging by the book, that should return me "Hi" right?
> Because I say: if a is equal to "dad" or "mom" say "Hi". I don't know if
> is my OS( Windows XP SP3( I've had several troubles with it )) or if is
> the last version of Ruby, which I am using, the 1.9.3 or what...
>  I'll appreciate your time guys, thanks.

The || operator returns the left operator if it is a true value (everything 
except nil and false) and the right operand if the left one is a false value. 
Since "dad" is a true value, that's what || will return. The if expression 
will be equivalent to:

if a == "dad"

What you want is:

if a == "dad" || a == "mom"

I hope this helps

Stefano