调用函数时F#类型不匹配 [英] F# type mismatch while calling function

问题描述

此代码

let rec readNLines n list =
 if n = 0 then
  list
 else 
  readNLines(n-1,readInt()::list)

以

Type mismatch. Expecting a 'a but given a 'a -> 'a    
The resulting type would be infinite when unifying ''a' and
''a -> 'a' (using built-in F# compiler)

但是在最后一行更改为

  readNLines(n-1,(readInt()::list))

或

  readNLines(n-1)(readInt()::list)

问题是:为什么? :|

Question is: Why? :|

推荐答案

仅最后一个版本可以使用，因为readNLines带有两个参数，但是

Only the last version can work, because readNLines takes two arguments, but

readNLines (n - 1, readInt() :: list)

仅传递一个参数(这是一个由int和list组成的元组).

passes only one argument (which is a tuple consisting of an int and the list).

readNLines (n - 1) (readInt() :: list)

将它们作为两个单独的参数传递-区别在于使用逗号(元组)和空格(两个参数).

passes them as two separate arguments - the difference here is using the comma (tuple) and space (two arguments).

顺便说一句，当您使用更多的空格时(就像我一样)，这将变得更加清晰，因为各个元素都更易于识别.

By the way, that becomes much clearer when you use more whitespace (as I did), because the individual elements are easier to identify.

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