RosettaCodeData/Task/Exponentiation-operator/Ela/exponentiation-operator-1.ela
2016-12-05 22:15:40 +01:00

11 lines
277 B
Text

open number
_ ^ 0 = 1
x ^ n | n > 0 = f x (n - 1) x
|else = fail "Negative exponent"
where f _ 0 y = y
f a d y = g a d
where g b i | even i = g (b * b) (i `quot` 2)
| else = f b (i - 1) (b * y)
(12 ^ 4, 12 ** 4)