binomialCoefficient function Null safety

Implementation

double binomialCoefficient(double nr, double kr) {
  int n = nr.floor();
  int k = kr.floor();
  if (n != nr || k != kr || n < 0 || k < 0 || k > n) {
    throw CalculatorError(0);
  }
  k = min(k, n - k);
  if (k > 200) {
    // Enough to overflow the 15C
    return double.infinity;
  } else if (k == 1) {
    return nr;
  } else if (n > 10000) {
    if (k > 36) {
      // Enough to overflow the 15C
      return double.infinity;
    }
    final kd = k.toDouble();
    return permutations(nr, kd, initial: 1.0 / factorial(kd));
  }

  final c = Float64List(k + 1);
  c[0] = 1;
  for (int i = 1; i <= n; i++) {
    for (int j = min(i, k); j > 0; j--) {
      c[j] += c[j - 1];
      if (c[j] == double.infinity) {
        return c[j];
      }
    }
  }
  return c[k];
}