From: Zsban Ambrus <ambrus@...>
Date: 2004-05-15T03:54:51+09:00
Subject: Re: Major Addition Bug?

On Fri, May 14, 2004 at 07:01:23AM +0900, Jeff Mitchell wrote:
> 
> This all suggests:
> 
> class FuzzyFloat
>    def initialize(value, epsilon)
>       @value = value
>       @epsilon = epsilon
>    end
> 
>    attr_reader :value, :epsilon
> 
>    def *(other)
>       FuzzyFloat.new(@value*other.value, @epsilon + other.epsilon)
>    end
>    
>    def ==(other)
>       distance = abs(@value - other.value)
>       (distance < @radius) and (distance < other.radius)
>    end
>    
>    # ...
> end
> 
> however there is a general problem of epsilon approaching the
> granularity of Float itself, i.e. the error of the error.  The Float
> version of Planck's constant confounds our measurements :) But
> FuzzyFloat may still have some use for sufficiently large epsilon.
> 

Why not do interval arithmetics?  Of course, you can't implement that in pure
ruby, only as a C addition, as you'll have to do arithmetic in different
rounding modes.

ambrus