OCaml模块类型和单独编译(OCaml module types and separate compilation)

 我正在阅读OCaml首席设计师1994年关于模块，类型和单独编译的论文。 （在另一个问题上 ， 诺曼拉姆齐指着我）。 我明白这篇论文讨论了OCaml目前模块类型/签名系统的起源。 就此而言，作者提出了对签名中的类型声明（允许单独编译）以及清单类型声明（为了表达）的不透明解释。 试图将我自己的一些示例放在一起来演示OCaml模块签名表示法试图解决的问题类型，我将以下代码写入两个文件中： 
 
 在文件.mli （或.mli - 我已经试过）（ 文件A ）： 
 
module type ORDERING = sig
 type t
 val isLess : t -> t -> bool
end
 
 并在文件useOrdering.ml （ 文件B ）中： 
 
open Ordering
module StringOrdering : ORDERING
  let main () =
    Printf.printf "%b" StringOrdering.isLess "a" "b"
  main ()
 
 这个想法是希望编译器抱怨（在编译第二个文件时）在模块StringOrdering中没有足够的类型信息来检查StringOrdering.isLess应用程序（从而激发对with type语法的需要）。 但是，虽然文件A按预期编译，但文件B会导致3.11.2 ocamlc抱怨语法错误。 我了解，签名是为了让某人根据模块签名编写代码，而无需访问实现（模块结构）。 
 
 我承认，我不确定语法： module A : B ，这是我在这篇相当老的论文中分别编译时遇到的问题，但它让我想知道是否存在这样或类似的语法（不涉及函数）以允许某人仅基于代码编写代码在模块类型上，在链接时提供实际的模块结构，类似于如何在C / C ++中使用*.h和*.c文件。 如果没有这种能力，看起来模块类型/签名基本上是用于密封/隐藏模块的内部或更明确的类型检查/注释，但不适用于单独/独立编译。 
 
 实际上，查看关于模块和单独编译的OCaml手册部分，似乎我与C编译单元的类比被破坏了，因为OCaml手册将OCaml编译单元定义为A.ml和A.mli二重奏，而在C / C ++ .h文件被粘贴到任何导入.c文件的编译单元。 

I am reading through OCaml lead designer's 1994 paper on modules, types, and separate compilation. (kindly pointed to me by Norman Ramsey in another question ). I understand that the paper discusses the origins of OCaml's present module type / signature system. It it, the author proposes opaque interpretation of type declarations in signatures (to allow separate compilation) together with manifest type declarations (for expressiveness). Attempting to put together some examples of my own to demonstrate the kind of problems the OCaml module signature notation is trying to tackle I wrote the following code in two files:
 
In file ordering.ml (or .mli — I've tried both) (file A):
 
module type ORDERING = sig
 type t
 val isLess : t -> t -> bool
end
 
and in file useOrdering.ml (file B):
 
open Ordering
module StringOrdering : ORDERING
  let main () =
    Printf.printf "%b" StringOrdering.isLess "a" "b"
  main ()
 
The idea being to expect the compiler to complain (when compiling the second file) that not enough type information is available on module StringOrdering to typecheck the StringOrdering.isLess application (and thus motivate the need for the with type syntax). However, although file A compiles as expected, file B causes the 3.11.2 ocamlc to complain for a syntax error. I understood that signatures were meant to allow someone to write code based on the module signature, without access to the implementation (the module structure).
 
I confess that I am not sure about the syntax: module A : B which I encountered in this rather old paper on separate compilation but it makes me wonder whether such or similar syntax exists (without involving functors) to allow someone to write code based only on the module type, with the actual module structure provided at linking time, similar to how one can use *.h and *.c files in C/C++. Without such an ability it would seem to be that module types / signatures are basically for sealing / hiding the internals of modules or more explicit type checking / annotations but not for separate / independent compilation.
 
Actually, looking at the OCaml manual section on modules and separate compilation it seems that my analogy with C compilation units is broken because the OCaml manual defines the OCaml compilation unit to be the A.ml and A.mli duo, whereas in C/C++ the .h files are pasted to the compilation unit of any importing .c file.

原文：https://stackoverflow.com/questions/9843378