From: Todd Benson <caduceass@...>
Date: 2008-09-15T01:08:39+09:00
Subject: Re: how do deal with huge numbers and keep them accurate?

On Sun, Sep 14, 2008 at 10:47 AM, Todd Benson <caduceass@gmail.com> wrote:
> On Sun, Sep 14, 2008 at 7:18 AM, Tomi Zzzz <tomi_z@nana.co.il> wrote:
>> Hello all, I wrote the following code:
>>
>> require "bigdecimal"
>> require "bigdecimal/math"
>> include BigMath
>> odd = gets.chomp.to_f
>> result = odd/3.0
>> puts result.to_f
>> blank = gets.chomp
>>
>> the code works just fine when the input is upto 15 digits, but
>> afterwards the code fails to give the correct output.
>>
>> a few good examples:
>> odd=1231231
>> result=410410.333333333
>>
>> odd=123123123123121    (15 digits)
>> result=41041041041040.3
>>
>> so far so good,now:
>> odd=1231231231231231   (16 digits)
>> result=4.1041041041041e+014     (given with no remainder)
>>   [It's a wrong answer! the result should have been  ---
>> 410410410410410.33333]
>>
>> What do i need to chance in the code to make it happen?
>> in the future i should deal with larger numbers and the accuracy is
>> essential.
>>
>> thanks in advanced, tomi.
>
> require 'bigdecimal'
> require 'bigdecimal/math'
> include BigMath
> a = BigDecimal('1231231231231231')
> b = 3.0
> puts a/b
> b = BigDecimal('3')
> puts a/b

Oops, didn't clarify.  What Rick said, but make sure your denominator
is also a BigDecimal instance.  Least common denominator operation
(Float object), I suppose.

Todd