project-euler/Sidef/188 The hyperexponentiation of a number.sf

#!/usr/bin/ruby

# Author: Daniel "Trizen" Șuteu
# Date: 14 August 2016
# License: GPLv3
# Website: https://github.com/trizen

# Find the last 8 digits of 1777↑↑1855.

# https://projecteuler.net/problem=188

# Runtime: 0.230s

func hyper(n, (1)) { n }

func hyper(n, k) {
    expmod(n, hyper(n, k-1), 1e8)
}

say hyper(1777, 1855)