Pisano period: Difference between revisions
→{{header|Haskell}}
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powMod :: Integral a => a -> a -> a -> a
powMod _ _ k | k < 0 = error "negative power"
powMod m _ _ | 1 == abs m = 0
powMod m p k | 1 == abs p = if 1 == p || even k then mod 1 m else mod p m
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