Question

加载此文件时出现此程序问题：

hanoi :: Integer -> Peg -> Peg -> Peg -> [Move]
hanoi 0 _ _ _ = []
hanoi n a b c =
let 
step1move = hanoi (n-1) a c b
step2move = (a,b)
step3move = hanoi (n-1) c b a
in
step1move ++ [step2move] ++ step3move`

hanoi4 :: Integer -> Peg -> Peg -> Peg -> Peg -> [Move]
hanoi4 0 _ _ _ _ = []
hanoi4 n a b c d =
let 
(half1,half2) = segment n
step1 = hanoi4 half1 a c b d
step2 = hanoi half2 a d b
step3 = (a, b)
step4 = hanoi half2 d b a
step5 = hanoi4 half1 c b a d
in
step1 ++ step2 ++ [step3] ++ step4 ++ step5

-- Segment n into two "halves" such that half1 + half2 = n - 1
segment :: Integer -> (Integer, Integer)
segment n = let half1 = n div 2 in (half1, n half1=1)`

Answer 1

我看到三个问题。首先，您的函数定义需要缩进。（与大多数使用花括号和分号的C系列语言不同，Haskell的解析器使用空格来定义函数体和其他句法结构，如do-blocks。）所以代替：

hanoi n a b c =
let
...

你需要：

hanoi n a b c =
  let
  ..

其次，你有两个迷失反引号（`）字符。

第三，你的segment函数定义看起来好像有一些错误的字符：

-segment n = let half1 = n div 2 in (half1, n half1=1)`
+segment n = let half1 = n div 2 in (half1, n-half1-1)

在河内塔解析错误（可能是不正确的缩进或括号不匹配）

1 个答案: