/**

* @function DoubleFactorialIterative

* @description Calculate the double factorial of a number (iterative implementation)

* @summary In mathematics, double factorial of a number n is denoted by n!!.

* It is not to be confused with (n!)!, which is the factorial function iterated twice.

* The double factorial is the product of all positive integers upto n that have the same parity (odd or even)

* as n.

* Therefore,

* 9!! = 9 . 7 . 5 . 3 . 1

* 10!! = 10 . 8 . 6 . 4 . 2

*

* Please note that for factorials of even numbers, the series ends at 2.

* @see [Wikipedia](https://en.wikipedia.org/wiki/Double_factorial)

* @see [Mathworld](https://mathworld.wolfram.com/DoubleFactorial.html)

* @see [GeeksForGeeks](https://www.geeksforgeeks.org/double-factorial/)

* @example DoubleFactorialIterative(4) = 8

* @example DoubleFactorialIterative(5) = 15

*/

const DoubleFactorialIterative = (n: number) => {

if (n < 0) throw new RangeError('The number needs to be non-negative')

let doubleFactorial = 1

for (let i = n; i > 0; i -= 2) doubleFactorial *= i

return doubleFactorial

}

export { DoubleFactorialIterative }