From: Robert Brown <rob99brown@...>
Date: 2007-07-17T08:34:33+09:00
Subject: Force calculation result to BigDecimal

Hi all,

I'm doing some complex math which I need to be based on BigDecimal
accuracy (not Float).  It seems that ruby defaults to Float when there's
a mixture of type in there, e.g.

Code :

   1. irb(main):001:0> require 'bigdecimal'
   2. => true
   3. irb(main):002:0> a = 5.123
   4. => 5.123
   5. irb(main):003:0> b = BigDecimal("6.789")
   6. => #<BigDecimal:8b4c0,'0.6789E1',8(8)>
   7. irb(main):004:0> c = a * b
   8. => 34.780047
   9. irb(main):005:0> c.class
  10. => Float

Is there a way I can force a BigDecimal outcome.

One way I guess would work is to make sure all args in the calculation
are BigDecimal, but that's a bit tiresome.  For a start, I'd have to
type check each arg and convert to BigDecimal if it was not BigDecimal -
that's gotta be slow...

On a related note, how do I initalize a BigDecimal from a Float (without
converting to string first).  How could I extend BigDecimal for this?


Thanks,



Rob

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