Ruby on Rails

On 24 December 2010 16:36, Marnen Laibow-Koser <lists@ruby-forum.com> wrote:
> Colin Law wrote in post #970510:
>> On 24 December 2010 14:47, Marnen Laibow-Koser <lists@ruby-forum.com>
>> wrote:
>>>> Talking slight bollocks. I meant that you can't store with infinite
>>>> precision, ie you'll always be liable for some error.
>>>
>>> Of course. You know a better way? Should we just store everything as
>>> Rational?
>>
>> For things that _are_ decimal numbers (such as money) use Fixed or
>> BigDecimal and for things that are not decimal then use Float and
>> determine the errors if it is important.
>
> That's basically what I've been saying, except for "decimal" substitute
> "rational".  However, there's not always an a priori way to determine if
> a given field will need to store irrational numbers.

I am not quite sure that is that is the same as "never, ever use
Floats for arithmetic" :)

Also as we have seen for rational numbers like 1/3 BigDecimal is no
better than float, except that it is possible to specify a smaller or
larger precision than that which float supplies, and it is a decimal
precision rather than a binary one.

Colin

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