Number formatting in Scala?

Question

I have a dynamically changing input reading from a file. The numbers are either Int or Double. Why does Scala print .0 after every D

Answer 1

scala> "%1.0f" format 1.0
res3: String = 1

If your input is either Int or Double, you can do it like this:

def fmt(v: Any): String = v match {
  case d : Double => "%1.0f" format d
  case i : Int => i.toString
  case _ => throw new IllegalArgumentException
}

Usage:

scala> fmt(1.0)
res6: String = 1

scala> fmt(1)
res7: String = 1

scala> fmt(1.0f)
java.lang.IllegalArgumentException
        at .fmt(:7)
        at .(:6)
        at .()
        at RequestResult$.(:4)
        at RequestResult$.()
        at RequestResult$result()
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.Dele...

Otherwise, you might use BigDecimals. They are slow, but they do come with the scale, so "1", "1.0" and "1.00" are all different:

scala> var x = BigDecimal("1.0")
x: BigDecimal = 1.0

scala> x = 1
x: BigDecimal = 1

scala> x = 1.0
x: BigDecimal = 1.0

scala> x = 1.000
x: BigDecimal = 1.0

scala> x = "1.000"
x: BigDecimal = 1.000