From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-11-10T22:33:58+09:00
Subject: Re: "puts, if and unless" VS "nil"

On Wed, Nov 10, 2010 at 2:26 PM, Edmond Kachale
<edmond.kachale@baobabhealth.org> wrote:
> Rubysters,
>
> I was sharing with some friends how to use if and unless. I wrote this
> statement: *puts nil if nil*
> and I got =>nil. (Which implies nothing was printed.)
>
> When I wrote: *puts nil unless nil*
> I got:
> nil
> => nil
> Which implies that puts output nil.
>
> My question is what is in *"nil"* that makes "*puts*" print "*nil"*? Or is
> there any explanation to back this behaviour?

It's in the implementation of puts:

http://ruby-doc.org/core/classes/IO.src/M002252.html

 if (NIL_P(argv[i])) {
            line = rb_str_new2("nil");
        }

It specifically checks for nil arguments and prints "nil" in that case.

Jesus.