From: Robert Klemme <shortcutter@...>
Date: 2007-07-17T22:32:27+09:00
Subject: Re: Force calculation result to BigDecimal

2007/7/17, Todd Benson <caduceass@gmail.com>:
> On 7/17/07, Robert Klemme <shortcutter@googlemail.com> wrote:
>
> > Hm....  I don't think this is a fix because once you have a float you
> > lost all the precision.
>
> Can you elaborate on this?  I was under the impression that converting
> to BigDecimal before arithmetic operations would get around this.

Actually you are right.  I somehow thought you intended #big to be
called on the result, i.e. after the calculation. Stupid me.  Sorry
for the confusion.

> Using
> class Float
>   def big; BigDecimal(self.to_s); end
> end
> irb > Math::PI.big * 2.0
> => 6.283185307178
> irb > Math::PI.big * 2.0.big
> => #<BigDecimal:81c2b88,'0.6283185307 17958E1',20(36)>
>
> > A better fix is probably to change #coerce to
> > work properly. Another solution is to make sure all values are
> > converted to BD before starting the calculation.
>
> This would be the best solution (maybe through #induced_from?), but I
> don't know how to do it.

It would take me too much time ATM to do it and it should also be
checked whether changing #coerce causes issues somewhere else...

Kind regards

robert