From: Rudolf Polzer <denshimeiru-sapmctacher@...>
Date: 2003-08-11T06:15:17+09:00
Subject: Re: Ruby and OOP-design (question of an old "procedural person" ;)

Scripsit ille �Brian Candler� <B.Candler@pobox.com>:
> On Mon, Aug 11, 2003 at 02:02:33AM +0900, dblack@superlink.net wrote:
> > > Does ruby not have exclusive or? I can't remember at the moment. If it
> > > did, I think the top is the same
> > > as:
> > >
> > > unless a.nil? ^ b.nil?
> > >
> > > Which is still somewhat unclear, I agree.
> > 
> > I, however, no long agree with myself :-)  I just forgot about ^.
> 
> However ^ is overloaded, so although it works when comparing false/true with
> false/true, it doesn't with other things; especially since it doubles up as
> a bitwise numeric operator too.

BTW: why do all C-like languages lack the ^^ operator (boolean XOR)?

> irb(main):001:0> 5 ^ false
> TypeError: cannot convert false into Integer
>         from (irb):1:in `^'
>         from (irb):1
> 
> But it does treat 'nil' as 'false'. So you could say:
> 
>      if  (a && true) ^ (b && true)

if !a ^ !b # since   a xor b == (not a) xor (not b)

Well, my common C idioms for this case are:

  boolean XOR:             !a ^ !b
  obfuscated boolean XOR:  !a!=!!!b /* no, I am not using that */
  convert to boolean:      !!a

They all work in Ruby.


-- 
L: N�per er�t medic�s nunc �st visp�llo Di�ulus:
   D: Fr�her war er Arzt, nun ist Diaulus Totengr�ber:
L: Qu�d visp�llo fac�t - f�cerat �t medic�s.
   D: Was er als Totengr�ber macht - tat er schon als Arzt.    [Martial]