From: Colin Bartlett <colinb2r@...>
Date: 2011-01-12T23:58:10+09:00
Subject: Re: :: -- operator or not?

On Wed, Jan 12, 2011 at 3:27 AM, David Masover <ninja@slaphack.com> wrote:
> On Tuesday, January 11, 2011 05:16:24 pm Kedar Mhaswade wrote:
>> ... The Ruby Programming Language says it is not an operator
>> because the righthand side is not a value or expression but an identifier.
>> So, is :: an operator or not?
>
> I would say no, because as far as I can tell, it can't be overloaded. Every
> other operator can be overloaded in some context.
> ...
> It's a fine semantic difference, though -- I don't think it matters whether
> it's an operator or not.

I agree. (Duck typing???)

But trying to be picky, the "definition" from The Ruby Programming
Language implies that a (binary) operator can operate on (two)
arbitrary expressions, but that :: expects the second operand to be a
constant or a method. So I'm not convinced that it's whether or not an
operator can be overloaded that is relevant, as Anurag Priyam
observed.

The following seems to bear this out, although I'm a bit puzzled why
"Q  ::I" and "Q  ::  I" fail, but "(Q)  ::  I" and "q  ::  I" work.

class Q
  p Q                       #=> Q
  q = Q
  p q                       #=> Q
  P = 355; I = 113
  p Q::I                    #=> 113
  p Q::  I                  #=> 113
  (p (Q  ::I))   rescue (p $!) #=> #<NameError: uninitialized constant I>
  (p (Q  ::  I)) rescue (p $!) #=> #<NameError: uninitialized constant I>
  p( (Q)  ::  I )           #=> 113
  p q  ::  I                #=> 113
  i = I
  p i                       #=> 113
  (p Q::i) rescue (p $!)
                #=> #<NoMethodError: undefined method `i' for Q:Class>
end