Ruby on Rails

On 23 December 2010 03:41, Marnen Laibow-Koser <lists@ruby-forum.com> wrote:
> TomRossi7 wrote in post #970207:
>> Any idea why this calculates the integer the way it does?
>>
>> irb> ("291.15".to_f * 100.0).to_i
>> => 29114
>
> Because of the vagaries of floating-point arithmetic:
> irb> ("291.15".to_f * 100.0) < 29115
> => true
> irb> printf "%.30f", ("291.15".to_f * 100.0)
> 29114.999999999996362021192908287048
>
> It bears repeating: never, ever use Floats for arithmetic.  If you can't
> use fixed-point math, then use BigDecimal.

I have to disagree here. I would rephrase it as _almost_ never use
Floats The one time when they would be appropriate is if you have a
large amount of arithmetic to perform. The sort of thing that might
occur in complex statistical analysis for example or engineering
calculations of some sort. On most (possibly all) computers floating
point consumes vastly less processor time to perform than BigDecimal.
This is a rare occurence in Rails apps I expect so I agree that for
most people Marnen's advice would be appropriate.

Colin

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