In Scala, how do you define a local parameter in the primary constructor of a class?

Question

In Scala, how does one define a local parameter in the primary constructor of a class that is not a data member and that, for example, serves only to initialize a data membe

Answer 1

If you remove the "var" or "val" keyword from the constructor parameter, it does not produce a property.

Be aware, though, that non-var, non-val constructor parameters are in-scope and accessible throughout the class. If you use one in non-constructor code (i.e., in the body of a method), there will be an invisible private field in the generated class that holds that constructor parameter, just as if you made it a "private var" or "private val" constructor parameter.

Addendum (better late than never??):

In this code the references to the constructor parameter occur only in the constructor body:

class C1(i: Int) {
  val iSquared = i * i
  val iCubed = iSquared * i
  val iEven = i - i % 2
}

... Here the value i exists only during the execution of the constructor.

However, in the following code, because the constructor parameter is referenced in a method body—which is not part of the constructor body—the constructor parameter must be copied to a (private) field of the generated class (increasing its memory requirement by the 4 bytes required to hold an Int):

class C2(i: Int) {
  val iSquared = i * i
  val iCubed = iSquared * i
  val iEven = i - i % 2

  def mod(d: Int) = i % d
}