Vala Tutorial: Variable-Length_Argument_Lists

Varargs.vala

/**
 * Varargs.vala
 *
 * @see https://wiki.gnome.org/Projects/Vala/Tutorial#Variable-Length_Argument_Lists
 *
 *
 * valac Varargs.vala
 * ./Varargs
 *
 */

class Actor1 {
  public void animate(int fixed, ...) {
    var l = va_list();
    while (true) {
        string? key = l.arg();
        if (key == null) {
            break;  // end of the list
        }
        double val = l.arg();
        stdout.printf("%s: %g\n", key, val);
    }
  }
}

class Actor2 {
  public void animate(int fixed, ...) {
    var l = va_list();
    while (true) {
        string? key = l.arg();
        if (key == null) {
            break;  // end of the list
        }
        double val = l.arg();
        stdout.printf("%s: %g\n", key, val);
    }
  }
}


public static int main(string[] args) {

  var actor1 = new Actor1();
  stdout.printf("string - double argument pairs\n");
  actor1.animate (3000, "x", 100.0, "y", 200.0, "rotation-angle-z", 500.0, "opacity", 0.0);

  /* Output -
  string - double argument pairs
  x: 100
  y: 200
  rotation-angle-z: 500
  opacity: 0
  */

  var actor2 = new Actor2();
  stdout.printf("Alternate\n");
  actor2.animate (3000, x: 100.0, y: 200.0, rotation_angle_z: 500.0, opacity: 0.0);

  return 0;
}