Divide two BigInt values and cast the result to Float in Scala

Question

I have a data frame which contains two columns of type BigInt . Then I have a user-defined function which performs an operation over these two columns and the final result is supposed to be of type Float .

def generateNewColumnValue(firstColumnValue: BigInt, secondColumnValue: BigInt): Float = {
   val calculated = scala.math.pow(firstColumnValue.toFloat / secondColumnValue, 1.0/3.0);
   return calculated;
}

val generateNewColumnValueUDF = udf[Float, BigInt, BigInt](generateNewColumnValue);

Inside of the body of the UDF I am doing some very simple calculations, as you can see. The problem is that I get the following error and I don't understand why it is not possible:

command-836521033094408:9: error: overloaded method value / with alternatives:
  (x: Double)Double <and>
  (x: Float)Float <and>
  (x: Long)Float <and>
  (x: Int)Float <and>
  (x: Char)Float <and>
  (x: Short)Float <and>
  (x: Byte)Float
 cannot be applied to (BigInt)
  val calculated = scala.math.pow(firstColumnValue.toFloat / secondColumnValue, 1.0/3.0);

The problem is that if I try to cast it to a lower range type (like Int) I might be losing some value after the decimal point.

Answer 1

The message just says you can divide a Float by Double , Float , etc. but not by BigInt . Call toFloat on both operands, not just one:

firstColumnValue.toFloat / secondColumnValue.toFloat

But math.pow takes Double s, not Float s, so toDouble makes more sense. If the result has to be Float , call toFloat on the result of pow , not its arguments.

Or going through BigDecimal :

(BigDecimal(firstColumnValue) / BigDecimal(secondColumnValue)).toDouble

In most cases it should give approximately the same result as the first option, but slower; the problem is that BigInt s can be so large that firstColumnValue.toDouble returns Double.PositiveInfinity / NegativeInfinity . You could check for that, and only use the second option in that case.