From: "Iñaki Baz Castillo" <ibc@...>
Date: 2008-05-02T23:25:55+09:00
Subject: Re: | versus || Any reason for this issue?

2008/5/2, Robert Klemme <shortcutter@googlemail.com>:
> On 02.05.2008 16:01, Iñaki Baz Castillo wrote:
>
> > Hi, why in the second case the non declared "my_var" variable is
> > processed but not in the first case?
> >
>
>  Because || does short circuit while | does not.
>
>
> > irb> nil || 2 || my_var
> > => 2
> >
> > irb> nil | 2 | my_var
> > NameError: undefined local variable or method `my_var'
> >
> > Of course, I prefer the first case: 2 is already true so there is no
> > reason to read the next "my_var". Also, it's not good for performance,
> > is it?
> >
>
>  "||" is the short circuit boolean "or" operator.  You cannot override it.
> "|" on the other hand is an operator that can be overloaded and it does not
> short circuit.  It would not make any sense to make "|" short circuit
> because it can contain arbitrary functionality.
>
>  Here are some classes that implement "|":
>
>  $ ruby -e 'ObjectSpace.each_object(Module) {|cl| p cl if
> cl.instance_methods.include? "|"}'
>  Array
>  Bignum
>  Fixnum
>  FalseClass
>  TrueClass
>  NilClass


Thanks to all for those excellent explanations :)


-- 
Iñaki Baz Castillo
<ibc@aliax.net>