"puts, if and unless" VS "nil"

Ruby
1

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?

Edmond
Software Developer | Baobab Health Trust (http://www.baobabhealth.org/)
|
Malawi

Cell: +265 999 465 137 | +265 881 234 717

*“Leading the Improvement of Health through Information and
Communication
Technology in the Developing World” The *Creed of *Baobab Health
*

2

On Wed, Nov 10, 2010 at 2:26 PM, Edmond K.
[email protected] wrote:

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.

3

2010/11/10 Jess Gabriel y Galn [email protected]:

nil
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™ Client VM 1.6.0_21) [x86-java]
nil
14:39:43 $

Kind regards

robert

4

On Wed, Nov 10, 2010 at 2:40 PM, Robert K.
[email protected] wrote:

I got:

========================================
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™ 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.