From: Walton Hoops <walton@...>
Date: 2009-11-28T15:06:17+09:00
Subject: Re: where is grep?

> From: Ruby Newbee [mailto:rubynewbee@gmail.com]
> 
> Thanks, that sounds be more reasonable, b/c I like to grep from an
> array not a string (yes perl does this).
> 
> btw, why 0/0 got failed but 0.0/0.0 seems valid?
> 
> irb(main):144:0> v=0/0
> ZeroDivisionError: divided by 0
>         from (irb):144:in `/'
>         from (irb):144
>         from /usr/bin/irb:12:in `<main>'
> 
> irb(main):145:0> v=0.0/0.0
> => NaN

It's the difference betweeen floating point and integer arithmetic.
When working with integers all results must be valid integers, whereas
floating point can represent NaN (Not a Number), negative zero,
and infinity and negative infinity:

irb(main):001:0> 1.0/0.0
=> Infinity
irb(main):002:0> -0.0
=> -0.0
irb(main):003:0> 0.0/-0.0
=> NaN
irb(main):004:0> -1.0/0.0
=> -Infinity
irb(main):005:0>

See http://en.wikipedia.org/wiki/Floating_point for more information.