From: Eleanor McHugh <eleanor@...>
Date: 2008-07-02T21:05:08+09:00
Subject: Re: Arithmetic oddity

On 2 Jul 2008, at 12:30, Minh Tran wrote:
>>> l = [1.0, 1.0, 2.0**0.5]
> => [1.0, 1.0, 1.4142135623731]
>>> s = l.map {|e| e**2}
> => [1.0, 1.0, 2.0]
>>> puts 'foo' if s[2] == s[1] + s[0]
> => nil
>>> puts 'foo' if 2.0 == 1.0 + 1.0
> foo
> => nil
>
> Does anyone know why s[2] == s[1] + s[0] is false ?

If you check in IRB you'll find that ((2.0 ** 0.5) ** 2.0) == 2.0  
returns false. That will be due to rounding errors in performing the  
sequence of floating point operations.


Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net
----
raise ArgumentError unless @reality.responds_to? :reason