acerix / cnum

 * Find the greatest common denominator of the two numbers.

 */

export const gcd = (a: bigint, b: bigint): bigint => {

  if (b === 1n || a === 1n) {

    return 1n

  }

  while (b !== 0n) {

    //[a, b] = [b, a % b] // not pretty???

    const t = a % b

    a = b

    b = t

  }

  return a < 0n ? -a : a

}

/**

 * Returns true if the number is prime.

 */

export const isPrime = (n: bigint): boolean => {

  if (n === 1n) return false

  for (let i = 2n; i * i <= n; i++) {

    if (n % i === 0n) return false

  }

  return true

}

  }

}

/**

 * Finds the prime factors, returning them in ascending order as arrays with their exponent as the second element.

 */

export const primeFactors = (n: bigint): Array<[bigint, bigint]> => {

  const f: Array<[bigint, bigint]> = []

  for (const p of primes()) {

    let e = 0n

    while (n % p === 0n) {

      e++

      n /= p

    }

    if (e) f.push([p, e])

    if (n === 1n) break

  }

  return f

}