RosettaCodeData/Task/Modular-exponentiation/Crystal/modular-exponentiation.cr

26 lines
511 B
Crystal

require "big"
module Integer
module Powmod
# Compute self**e mod m
def powmod(e, m)
r, b = 1, self.to_big_i
while e > 0
r = (b * r) % m if e.odd?
b = (b * b) % m
e >>= 1
end
r
end
end
end
struct Int; include Integer::Powmod end
a = "2988348162058574136915891421498819466320163312926952423791023078876139".to_big_i
b = "2351399303373464486466122544523690094744975233415544072992656881240319".to_big_i
m = 10.to_big_i ** 40
puts a.powmod(b, m)