From: David Masover <ninja@...>
Date: 2009-12-31T12:12:17+09:00
Subject: Re: Why can't I use "or" here?

On Wednesday 30 December 2009 08:35:43 pm Phillip Gawlowski wrote:
> On 31.12.2009 03:24, Albert Schlef wrote:
> > (The problem is in both Ruby 1.8 and Ruby 1.9)
> >
> > The expression:
> >
> >    puts(nil || 4)
> >
> > works as expected. It prints '4'.
> >
> > But this expression:
> >
> >    puts(nil or 4)
> >
> > fails... it is a syntax error, for some mysterious reason.
> >
> > Why? I thought the only diference between "or" and "||" is the
> > precedence.
> 
> Hm, on Ruby 1.9.1 I get:
> irb(main):001:0> puts nil or 4
> 
> => 4
> irb(main):002:0> puts(nil or 4)
> SyntaxError: (irb):2: syntax error, unexpected keyword_or, expecting ')'
> puts(nil or 4)
>             ^
>          from C:/Ruby19/bin/irb:12:in `<main>'
> irb(main):003:0> puts(nil || 4)
> 4
> => nil

Specifically, the parens around the method call. Want to see something even 
weirder?

irb(main):001:0> puts(nil or)
SyntaxError: (irb):1: syntax error, unexpected keyword_or, expecting ')'
puts(nil or)
           ^
        from /home/ruby19/bin/irb:12:in `<main>'
irb(main):002:0> puts(nil or 4)
SyntaxError: (irb):2: syntax error, unexpected keyword_or, expecting ')'
puts(nil or 4)
           ^
        from /home/ruby19/bin/irb:12:in `<main>'
irb(main):003:0> (nil or 4)
=> 4
irb(main):004:0> puts((nil or 4))
4
=> nil
irb(main):005:0>