title: NSDecimalNumber for big number operations on iPhone
body: <p>I need to use big number for precision in my application, float or double are not enough.
  I also have int and float numbers, and I have to do operations with all of them.</p>
  
  <p>I think that NSDecimalNumber is good for the precision I need, but I would like to do operations with other kind of numbers and it is complex formula. So I doesn't look appropriate to use this class in order to do complex formulas (too complicated to use the functions decimalWith... or decimalBy...) when you have lots of things.</p>
  
  <p>Does anyone know what to use in order to manipulate big numbers easily, and do operations on them with different types (float, decimal, int)?</p>
  
  <p>Thank you.</p>