From: Kyle Schmitt <kyleaschmitt@...>
Date: 2007-09-02T05:33:17+09:00
Subject: Re: 0.06 == 0.06 returns false in Ruby?

On 8/31/07, Logan Capaldo <logancapaldo@gmail.com> wrote:
> On 8/31/07, Kyle Schmitt <kyleaschmitt@gmail.com> 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.
> >
> Um, 2's compliment is not a cause of floating point error. IEEE
> floating point numbers do not use two's complement, they have a sign
> bit. Two's complement is just a way of encoding the sign of a value.

Used the wrong term :P sue me.  I guess that's why I should lookup
stuff before responding ;)
Anyway it's all based on the fact that you can't store some numbers
exactly as sum of different xes for 2**(-x).

--Kyle