From: Aldric Giacomoni <"aldric[removeme]"@...>
Date: 2009-04-11T05:10:08+09:00
Subject: Re: Float.finite ?

Ah! Understood. Thank you.. Big help :)

Stefano Crocco wrote:
> Alle Friday 10 April 2009, Aldric Giacomoni ha scritto:
>> How does one use .finite? effectively? I tried with (1.0/3).finite? =>
>> true... I tried with BigDecimal.. Still true. I'm pretty sure these numbers
>> aren't finite. How do I make this work?
> 
> According to the ri documentation, Float#finite? only returns false if self is 
> not inifinite and self.nan? is false. For example,
> 
> (1/0.0).finite?
> => false
> 
> What you wanted to know is whether the number has a finite or infinite number 
> of decimal digits. Unfortunately, I don't think such a method exists. You 
> can't do that with floats, because all floats have a finite number of decimal 
> digits (you can't very well store infinite digits in your computer's memory, 
> after all). I suppose it can be done with the Rational class, but you'd have 
> to write the method yourself. Here's a simple example of how this could be 
> done:
> 
> require 'rational'
> 
> class Rational
> 
>   def finite_digits?
>     d = denominator
>     return false if d % 2 !=0 and d % 5 != 0
>     d = d / 2 while d % 2 ==0
>     d = d / 5 while d % 5 == 0
>     d == 1
>   end
>   
> end
> 
> Stefano
> 

-- 
Aldric Giacomoni<br>
   Sometimes one should just look at things and think about things without
doing things.	  -- Calvin