Why do we need to pass numbers in exponential form for Double in Scala?

Question

I have executed the below sample program in Scala with different parameters.

object TestScalaWS {
  println("Welcome to the Scala worksheet")       //> Welcome to the Scala worksheet
  3+5                                             //> res0: Int(8) = 8
  1.0E5                                           //> res1: Double(100000.0) = 100000.0
  def abs(x: Double) = if (x<0) - x else x        //> abs: (x: Double)Double

  def sqrtIter(guess: Double, x: Double):Double =
     if (isGoodEnough(guess,x)) guess
     else sqrtIter(improve(guess,x),x)            //> sqrtIter: (guess: Double, x: Double)Double

  def isGoodEnough(guess: Double, x: Double) =
     abs(guess*guess-x) < 0.001                   //> isGoodEnough: (guess: Double, x: Double)Boolean

  def improve(guess: Double, x:Double) =
      (guess + x/guess)/2                         //> improve: (guess: Double, x: Double)Double


  def sqrt(x:Double) = sqrtIter(1.0,x)            //> sqrt: (x: Double)Double
  sqrt(2)                                         //> res2: Double = 1.4142156862745097
  sqrt(4)                                         //> res3: Double = 2.0000000929222947
  sqrt(0.001)                                     //> res4: Double = 0.04124542607499115
  sqrt(0.1e-20)                                   //> res5: Double = 0.03125
  sqrt(0.1e20)                                    //> res6: Double = 3.1622776601683793E9
  sqrt(1.0e20)                                    //> res7: Double = 1.0E10
  sqrt(1E9)                                       //> res8: Double = 31622.776601684047
  sqrt(1000000000)                                //> res9: Double = 31622.776601684047
  sqrt(1E10)                                      //> res10: Double = 100000.0
}

But sqrt(10000000000) which is equivalent to 1E10 giving error as "integer number too large" in Scala IDE even I have declared x as Double.

I assume there is some compiler interpret issue but don't know what exactly it means. Is this problem only in Scala ? or exist in Java too. ? or problem with Scala IDE?

Thanks, Gopal.

Answer 1

When you type 10000000000 , you try to define an Int , same as when you type 1 or -35 .

When you type sqrt(2) , your Int is implicitly converted to a Double , since this is what your function expects, and such an implicit converter does exist.

However, when you type sqrt(10000000000) , it throws an exception at the first step: defining the integer 10000000000 which is a number larger than Ìnteger.MaxValue`.

What's important to understand is that the conversion to the type you want is done after:

• first defining a type for your input (here a number without dot or exponent is considered an Int )

• then parsing the input with the selected type rules (this is the step that throws in your case, because your number cannot be parsed as an Int )