[ruby-talk:02876] Re: Just one more wafer thin mint....

(This message has been sent to comp.lang.ruby and is posted here just in case not everybody reaches it)

In article <[e-mail]>,
  Yukihiro Matsumoto <[e-mail]> wrote:

<snip>

> |The reason people implement odd but not even is that odd is
> |unambiguous, but people seem to disagree about whether zero is even.
> 
> Really?  I learned 0 is a even when I was in elementary school.
> I thought it was a common sense.
> 
> 							matz.

"Andrew Hunt" <[e-mail]> replied in Ruby-Talk:

<snip>

> But how would you expect zero to work? I believe that zero 
> is considered even (something like: "an integer n is called *even* if 
> there exists an integer m such that n = 2m", so 0 = (2)(0) is even).

Actually, from my Calculus, I recall that 0 is not even considered a natural number...

N = {1, 2, 3, 4, ...}              # these are the natural numbers
Z = {0, 1, -1, 2, -2, 3, -3, ...}  # and these are the (real :) integers

(actually Z = N U -N U {0})

and the definition of even number is 2N = { n E N / n%2 = 0 } which only applies to natural positive numbers...

It's a matter of wholedness (no pun intended :), as when 0 enters into a definition, lots of definitions and tautologoes and theorems break...

Regarding adding the method, for the sake of small interfaces, I'd say (n%2 == 1) is short enough and obvious enough to a programmer to be just enough (aliteration and repetition by accident :)

just my E0.02 worth,
d@
--
<excalibor at demasiado.com>
<[e-mail]>
-------------------------------------------------------------
Mensaje enviado gracias al correo gratuito de Demasiado Corp.
[ http://correo.demasiado.com ]
-------------------------------------------------------------