From: Robert Klemme <shortcutter@...>
Date: 2010-11-10T22:40:39+09:00
Subject: Re: "puts, if and unless" VS "nil"

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 $

Kind regards

robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/