Mutable Variables

Like in many other languages, there are also mutable variables in Effekt. Whereas values are defined using the val keyword, mutable variables use the var keyword.

def sum(xs: List[Int]): Int = {
  var sum = 0
  xs.foreach { x =>
    sum = sum + x
  }
  sum
}

It is not permitted to have uninitialized variables, that is, there are no mere declarations of variables. Therefore, the following is not allowed:

def main() = {
  var x: Int; // ERROR: Expected = but got ;
  ()
}

At runtime, mutable variables are allocated on the stack – see also regions and captures.

Values Computations