From: Matthew Moss <matthew.moss.coder@...>
Date: 2006-01-26T06:26:32+09:00
Subject: Re: readable and provocative & daring

On 1/25/06, Richard Drake <rdrake98@gmail.com> wrote:
> Yes, and it was the ability to extend & to String that started as a
> 'what if?' this time last week and ended with some serious questions
> about how wide the utility of this version may be. Or perhaps Ruby
> veterans would vote it down for reasons I might not currently grasp?

Well, if you simply wanted to create a & method on String, that's easy:

class String
  def &(rhs)
    self + rhs
  end
end

If what you actually wanted is to make '&' short-circuit, that's a
whole 'nother problem that, IMO, is best left alone.  First, it flies
in the face of the traditional meaning from other long-lived
programming languages. (I'm very willing to discard or change
tradition if it makes gains on efficiency, readability, etc...  but I
highly disagree that making '&' short-circuit is worth it, especially
when Ruby has both '&&' and 'and'.)

Second, it could not be (simply) implemented with a standard method
call. The nature of calling a function is that its arguments are
evaluated.  Which means that 'rhs' in String.& above must be evaluated
before the function can be called.  So String.& cannot possibly
short-circuit.  (Related... If you read any good-programming-practices
book for C++, they warn against overloading operator&& and operator||
for specifically this reason: they cannot short-circuit.)

You could, possibly, redefine String.& like this:

class String
  def &(rhs)
    some_cond ? self + rhs : self
  end
end

And then, if rhs is an object that lazily evaluates, you might be able
to fake short-circuitness.  But I think it's not worth it that much...
 smells bad, probably better ways to do things.