A Callable class allows its instance to be called a function. This feature of Dart language helps make named functions.

You can use any class as a function. Just add a method call to it.

void main() {
  final mult = Multiplication(10);
  print(mult(2)); // 20
  print(mult(5)); // 50
  print(mult(-10)); // -100

class Multiplication {

  final num value;

  num call(num factor) => value * factor;