From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-11-11T02:33:20+09:00
Subject: Re: "puts, if and unless" VS "nil"

On Wed, Nov 10, 2010 at 2:40 PM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> 2010/11/10 Jesús Gabriel y Galán <jgabrielygalan@gmail.com>:
>> 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.
>
> This is highly version dependent!
>
> 14:38:33 $ allruby -e 'puts nil'
> CYGWIN_NT-5.1 padrklemme2 1.7.7(0.230/5/3) 2010-08-31 09:58 i686 Cygwin
> ========================================
> ruby 1.8.7 (2008-08-11 patchlevel 72) [i386-cygwin]
> nil
> ========================================
> ruby 1.9.1p429 (2010-07-02 revision 28523) [i386-cygwin]
>
> ========================================
> jruby 1.4.0 (ruby 1.8.7 patchlevel 174) (2009-11-02 69fbfa3) (Java
> HotSpot(TM) Client VM 1.6.0_21) [x86-java]
> nil
> 14:39:43 $

Ooops, forgot to mention I was answering for MRI 1.8.7, thanks.

Jesus.