Question

请原谅我滥用术语的可能性，我对OCaml仍然不太满意。

我们有一个带有以下（删节）签名的仿函数：

  module type FUNCTORA = sig
    type input
    type output
    type key
    type inter

    val my_function : input list -> (key * output) list Deferred.t

  end

接下来，我们这样实现它。 MYAPP与上述类型相同。

  module MyFunctor (App : MyAPP) : FUNCTORA = struct
    type input = App.input
    type output = App.output
    type key = App.key
    type inter App.value

    let my_function lst = ... 
  end

在尝试编译实现时，我们收到此错误：

   Error: Signature mismatch:
   ...
   Values do not match:
     val my_function :
       App.input list ->
       (App.key * App.output) list Async_kernel.Deferred.t
   is not included in
     val my_function :
       input list -> (key * output) list Async.Std.Deferred.t

即使我们将它们设置为相同的类型，它也不会考虑包含App.input等的输入。我们如何才能进行类型检查呢？

Answer 1

If I make the following changes:

MyAPP => FUNCTORA (* Since you say they are the same *)

type inter App.value  =>  type inter = App.inter (* Syntax/name error *)

Deferred.t => option (* To limit dependence on other modules *)

Then your code compiles for me.

Possibly the problem is with Deferred.t. There are two distinct looking types in the error message.

签名与模块/仿函数中的类型不匹配

1 个答案: