计算 Haskell 中自然数的指数

Question

data Nat = Zero | Succ Nat

在Haskell中，使用声明，如何计算自然数n和m的幂，n^m?

exponential :: Nat -> Nat

Answer 1

你可以通过先实现加法和乘法来制作它：

plus :: Nat -> Nat -> Nat
plus n Zero = n                    -- n + 0 = n
plus n (Succ m) = Succ (plus n m)  -- n + (m + 1) = 1 + (n + m)

mult :: Nat -> Nat -> Nat
mult n Zero = Zero                   -- n * 0 = 0
mult n (Succ m) = plus n (mult n m)  -- n * (m + 1) = n + n * m

expo :: Nat -> Nat -> Nat
expo n Zero = Succ Zero              -- n^0 = 1
expo n (Succ m) = mult n (expo n m)  -- n^(m + 1) = n * n^m

请注意，您描述的求幂类型应该是 Nat -> Nat -> Nat，而不是 Nat -> Nat。

计算 Haskell 中自然数的指数

Calculate the exponential of Natural Numbers in Haskell

haskell