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shkesar/Nat.hs

Created June 5, 2019 08:04
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Haskell Natural Numbers
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Nat.hs
-- Natural Numbers
data Nat = Zero | Succ Nat
instance Show Nat where
show Zero = "Zero"
show (Succ m) = printf "Succ (%s)" (show m)
nat2int :: Nat -> Int
nat2int Zero = 0
nat2int (Succ n) = 1 + nat2int n
int2nat :: Int -> Nat
int2nat 0 = Zero
int2nat n = Succ (int2nat (n-1))
add' :: Nat -> Nat -> Nat
add' Zero n = n
add' (Succ m) n = Succ (add' m n)
-- addNat :: Nat -> Nat -> Nat
-- addNat m n = int2nat (nat2int m + nat2int n)
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