Haskell 键入错误，出了什么问题？
我正在使用 Hugs 编译一个简单的 Haskell 函数来计算排列数。我希望它返回一个整数，但我需要对浮点数进行操作。 我尝试将答案计算为浮点型，然后将其截断，但由于某种原因它无法正常工作。
这是函数：
choose :: Float -> Float -> Integer
choose n r = truncate (chooseF (n r))
where
chooseF::Float->Float->Float
chooseF n r | n==r = 1
| otherwise = n / (n-r) * chooseF(n-1) r
这是错误（第 35 行是函数的第二行）：
ERROR "/homes/mb4110/SimpleMath":35 - Type error in application
*** Expression : n r
*** Term : n
*** Type : Float
*** Does not match : a -> b
这可能是我遗漏的明显内容，但我已经研究了很长一段时间并且想不出解决方案。
I'm using hugs to compile a simple Haskell function calculating the number of permutations. I would like it to return an Integer, but I need to operate on floats.
I've tried to calculate the answer as a Float and then truncate it, but for some reason it's not working out.
This is the Function:
choose :: Float -> Float -> Integer
choose n r = truncate (chooseF (n r))
where
chooseF::Float->Float->Float
chooseF n r | n==r = 1
| otherwise = n / (n-r) * chooseF(n-1) r
This is the Error (Line 35 is the second line of the function):
ERROR "/homes/mb4110/SimpleMath":35 - Type error in application
*** Expression : n r
*** Term : n
*** Type : Float
*** Does not match : a -> b
It's probably something obvious that I'm missing but I've been at this for a good while and can't think of the solution.
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chooseF采用两个参数，但由于括号n r被解析为单个参数。因此，删除n r周围的括号就可以了。chooseFtakes two arguments, but because of the parenthesisn ris parsed as a single argument. Thus, remove the parenthesis aroundn rand it should be fine.问题是您将
(nr)传递给chooseF。 Hugs 由此确定项n必须是a -> 类型的某个函数。 b，您要向其中传递r。然后，其结果将部分应用于chooseF。据推测，您希望使用
n和r作为参数来调用chooseF。要修复此错误，请改为调用chooseF n r。The problem is that you are passing
(n r)tochooseF. Hugs determines from this that the termnmust be some function of typea -> b, into which you are passingr. The result of this would then be partially applied intochooseF.Presumably, you wanted to call
chooseFwith bothnandras parameters instead. To fix this error, callchooseF n rinstead.