Dart currying

main.dart

void main() {  
  final sum2 = curry2((int a, int b) => a + b);
  final sum3 = curry3((int a, int b, int c) => a + b + c);
  
  print(sum2(1));
  print(sum2(1)(2));
  
  print(sum3(1));
  print(sum3(1)(2));
  print(sum3(1)(2)(3));
}


typedef Curry2<R, T1, T2> = R Function(T2) Function(T1);

Curry2<R, T1, T2> curry2<R, T1, T2>(R Function(T1, T2) fn) {
  return (T1 t1) => (T2 t2) => fn(t1, t2);
}

typedef Curry3<R, T1, T2, T3> = Curry2<R Function(T3), T1, T2>;

Curry3<R, T1, T2, T3> curry3<R, T1, T2, T3>(R Function(T1, T2, T3) fn) {
  return curry2((a, b) => (c) => fn(a, b, c));
}

typedef Curry4<R, T1, T2, T3, T4> = Curry3<R Function(T4), T1, T2, T3>;

Curry4<R, T1, T2, T3, T4> curry4<R, T1, T2, T3, T4>(R Function(T1, T2, T3, T4) fn) {
  return curry3((a, b, c) => (d) => fn(a, b, c, d));
}