haskell"exp"函数返回错误的结果

Question

以下代码:

Module Main where

main :: IO ()
main = do putStrLn "hello"
          putStrLn $ "2 exp 6 = " ++ show (2 `exp1` 6)

exp1 :: Integer -> Integer -> Integer
exp1 x n | n == 0 = 1
         | n == 1 = x
         | even n =     exp1 (x*x) m
         | odd  n = x * exp1 (x*x) (m-1)
         where m = n `div` 2

产生输出4的2 `exp1` 6,这显然是错误的.

谢谢

Answer 1

奇怪的是错误的.你最终会评估exp1 4 3成为4 * (exp1 16 0).