main.dart

add2Numbers(int number1, {required int number2}) {
 return number1 + number2;
}

add2NumbersNotReq([int number1 = 5, int number2 = 10]) {
 return number1 + number2;
}

add2NumbersNamedOptional({required int number1, int? number2}) {
  return number1 + (number2 ?? 0);
}

void main(){
  print(add2Numbers(2, number2: 5));
  print(add2NumbersNotReq());
  print(add2NumbersNamedOptional(number1: 0));
  print(add2NumbersNamedOptional(number1: 1, number2:1));
}