From: Ken Bloom <kbloom@...>
Date: 2007-09-01T01:10:11+09:00
Subject: Re: 0.06 == 0.06 returns false in Ruby?

On Sat, 01 Sep 2007 00:24:39 +0900, M. Edward (Ed) Borasky wrote:
> Kyle Schmitt wrote:
>> On 8/30/07, doug meyer <doug.meyer@sigeps.org> wrote:
>>> There is also a class called BigDecimal (or something like that) if
>>> you want to have really accurate numbers and no floating-point errors.
>> 
>> A warning on things like BigDecimal.
>> Unless I'm mistaken it's still stored in twos compliment, which means
>> you'll still end up with the same sort of floating point problems
>> (albeit further down), and the same numbers that you can't express
>> exactly with a normal float, can't be expressed exactly with a
>> BigDecimal.
>> 
>> You'd think some fixed point math libraries would help, but be careful,
>> because many of those _also_ store in twos compliment.
>> 
>> --Kyle
>> 
>> 
> IIRC BigDecimal is in fact stored in (pregnant pause) Binary Coded
> Decimal. But I should check that.

Neither one can represent 1/3 or sqrt(2) exactly.

-- 
Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/