factorial property

int factorial

Returns the factorial of this.

Implementation

int get factorial {
  if (this < 0) {
    throw ErrorOfType<InvalidFunctionParameter>(
      message: 'The getter factorial is not defined for negative numbers.',
      invalidState: '$this < 0.',
    );
  }
  if (this == 0) {
    return 1;
  } else {
    return _cache[this] ??= this * (this - 1).factorial;
  }
}