From: Charles Oliver Nutter <charles.nutter@...>
Date: 2008-08-24T11:14:22+09:00
Subject: Re: Why 'if 0' succeeds in Ruby

M. Edward (Ed) Borasky wrote:
> On Sun, 2008-08-24 at 02:31 +0900, Dave Bass wrote:
>> But unfortunately Ruby regards both false and nil as not-true. For some 
>> reason, this is touted as a feature.
>>
>> False and nil are two quite different concepts and should not be 
>> conflated.
> 
> Exactly! To make matters worse, Lisp "traditionally" treated nil as
> false, but Scheme has "true", "false" and "nil" and nil is treated as
> true in Scheme.
> 
> So I don't have a problem with 0 not being false, but I do have a
> problem with nil being false in Lisp and Ruby and true in Scheme. 0 is
> 0, nil is nil, true is true and false is false and that is that!

I tend to look at these things not from at the level of pedantic 
consistency-mongering but in terms of what would be lost if the concept 
were changed.

* a ||= x would no longer work, since unassigned a (nil) would not 
evaluate to false causing x to be assigned.

* @a ||= x would no longer work

* a[n] ||= x would no longer work

* a.b ||= x would no longer work

"nil" being considered a boolean false seems absolutely natural to me, 
and it makes possible a large number of concepts in Ruby we'd really miss.

- Charlie