From: Claus Spitzer <DocBoobenstein@...>
Date: 2004-05-21T00:07:02+09:00
Subject: Re: Zero is true ... whoda thunk?

On Thu, 20 May 2004 23:42:59 +0900, Carlos <angus@quovadis.com.ar> wrote:
> 
> [Claus Spitzer <DocBoobenstein@gmail.com>, 2004-05-20 02.53 CEST]
> 
> 
> > On Thu, 20 May 2004 09:47:07 +0900, Nicholas Van Weerdenburg
> > <nick@activehitconsulting.com> wrote:
> > >
> > > nonzero? returned nil instead of false for me. Shouldn't it return false?
> >
> > 8< ----- snip -----
> >
> > No. From the pickaxe:
> >
> > nonzero?  num.nonzero? -> num or nil
> >
> > Returns num if num is not zero, nil otherwise. This behavior is useful
> > when chaining comparisons:
> >
> > a = %w( z Bb bB bb BB a aA Aa AA A )
> > b = a.sort {|a,b| (a.downcase <=> b.downcase).nonzero? || a <=> b }
> > b  � ["A", "a", "AA", "Aa", "aA", "BB", "Bb", "bB", "bb", "z"]
> 
> But why shouldn't it return false instead of nil?
> 
> 

Well, it's just a matter of grammar. zero? could have been implemented
as returning nil or or 0 (since 0 is true), but that's not as neat and
tidy as true/false. On the other hand, nonzero? returns nil or the
actual number, and nil/number is a better pair than false/number. From
the programmer's view, it's neater to have false/true and nil/value
pairs, and unless you do something like
   if num.nonzero? == false
instead of 
   if num.zero?
then you won't really notice the difference. Cheers!
  -C