“错误:未绑定的模块"；在OCaml中 [英] "Error: unbound module" in OCaml

问题描述

这是使用库Cohttp的简单示例:

Here's a simple example of using the library Cohttp:

open Lwt
open Cohttp
open Cohttp_lwt_unix

let body =
  Client.get (Uri.of_string "http://www.reddit.com/") >>= fun (resp, body) ->
  let code = resp |> Response.status |> Code.code_of_status in
  Printf.printf "Response code: %d\n" code;
  Printf.printf "Headers: %s\n" (resp |> Response.headers |> Header.to_string);
  body |> Cohttp_lwt.Body.to_string >|= fun body ->
  Printf.printf "Body of length: %d\n" (String.length body);
  body

let () =
  let body = Lwt_main.run body in
  print_endline ("Received body\n" ^ body)

我正在尝试编译

 ocaml my_test1.ml

错误:

错误:未绑定的模块Lwt

Error: Unbound module Lwt

如何在我的应用程序中实际包含/要求模块Lwt?

更新

也:

$ ocamlbuild
bash: ocamlbuild: command not found

但是:

$ opam install ocamlbuild
[NOTE] Package ocamlbuild is already installed (current version is
       0.12.0).

还有

$ opam install ocamlfind
[NOTE] Package ocamlfind is already installed (current version is
       1.7.3-1).

还有

$ ocamlfind
bash: ocamlfind: command not found

ocamlfind和ocamlbuild在哪里?

Where are ocamlfind and ocamlbuild located?

更新2

$ ocamlfind ocamlc -package lwt -c my_test1.ml 
 File "my_test1.ml", line 2, characters 5-11:
 Error: Unbound module Cohttp

推荐答案

您可以根据需要选择几种方法.

You have several options depending on your needs.

1)如果您要为二进制文件创建一个完整的项目，建议您查看 jbuilder .这是一个非常好的指南，它逐步解释了环境/项目配置: OCaml对于急躁的人.

1) If you want to create a full project for your binary I recommend looking at jbuilder. Here is a very nice guide that explains the environment/project configuration step-by-step: OCaml for the impatient.

2)另一个选择是像您尝试的那样直接编译二进制文件:

2) Another option is to compile the binary directly as you were trying to do:

ocamlbuild -pkg lwt -pkg cohttp-lwt-unix my_test1.native

请注意，您需要有一个名为my_test1.ml的文件才能生成所请求的my_test1.native.

Note that you need to have a file named my_test1.ml to generate the requested my_test1.native.

3)最后，对于快速脚本，我发现可以方便地要求OCaml解释器将依赖项直接加载到源文件中非常方便.只需将以下内容添加到文件的开头即可:

3) And finally for quick scripts I find it handy to be able to ask the OCaml interpreter to load the dependencies directly in the source file. Just add the following to the beginning of your file:

#use "topfind";;
#require "lwt";;
#require "cohttp-lwt-unix";;

然后运行ocaml my_test1.ml.

希望这会有所帮助！ :)

Hope this helps! :)

还要查看您遇到的command not found错误，我建议您确保正确配置您的环境.真实世界的OCaml书籍为此提供了一个Wiki页面: https://github.com/realworldocaml /book/wiki/安装说明

Also looking at the command not found errors you are getting I can suggest to make sure your environment is correctly configured. The Real World OCaml book has a wiki page for that: https://github.com/realworldocaml/book/wiki/Installation-Instructions

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