nums function

List<int> nums(int a, [ int? b, int? step ])

Generate a List of integers

Implementation

List<int> nums(int a, [int? b, int? step]) {
  // if step==null
  List<int> numList(int a, [int? b]) {
    if (b != null) {
      if (b >= a) {
        return List.generate(b - a + 1, (index) => index + a);
      } else {
        return List.generate(a - b + 1, (index) => index + b).reversed.toList();
      }
    } else {
      if (a < 0) {
        return List.generate(-a, (index) => -index).reversed.toList();
      } else {
        return List.generate(a, (index) => index);
      }
    }
  }

  if (b == null && step == null) {
    return (numList(a));
  }
  if (b != null && step == null) {
    return numList(a, b);
  } else {
    if (step! <= 0) {
      throw ArgumentError('step must be greater than 0');
    }

    List<int> result = [];
    if (b! >= a) {
      for (int i = a; i <= b; i += step) {
        result.add(i);
      }
    } else {
      for (int i = a; i >= b; i -= step) {
        result.add(i);
      }
    }
    return result;
  }
}