一个haskell＆＃34; exp＆＃34;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

为4生成输出2 `exp1` 6，这显然是错误的。

感谢

Answer 1

奇怪的情况是错误的。您最终将exp1 4 3评估为4 * (exp1 16 0)。