Haskell：在WinGHCi中卸载模块 [英] Haskell : unload module in WinGHCi

问题描述

我加载了两个模块（NecessaryModule1.hs和NecessaryModule2.hs，链接在 Haskell：加载当前目录路径中的所有文件）。现在我想卸载NecessaryModule2.hs。我在 System.Plugins.Load 但是它在WinGHCi中不起作用。我得到的错误信息是：

 > unload NecessaryModule2 
 
< interactive>：1： 1：不在范围内：'unload'
 
< interactive>：1：8：
不在范围内：数据构造函数`必需的模块2'
  
 
 
 
我试过了 
 
 
  import System.Plugins.Load 
  
但没有奏效。有没有办法以上述方式卸载模块？
 
 
 
 ---------------------- -------------------------------------------------- --------------- 
 
 
 
 [对Riccardo的回应] 
 
 
 
您好Riccardo，我尝试了您的建议，但我无法在WinGHCi中使用它。我有一个文件NecessaryModule1.hs如下：
 
 
  module NecessaryModule1其中
 
 addNumber1 :: Int  - > Int  - > Int 
 addNumber1 ab = a + b 
  
我通过'：cd'命令，然后执行： 
 
 
 > ：module + NecessaryModule1 
 
<无位置信息>：
找不到模块'NecessaryModule1'：
它不是当前程序中的模块，也不是任何已知的程序包。 
  
这是正确的吗？谢谢 
 
 
 
 -------------------------- -------------------------------------------------- ----------- 
 
 
 
 [更正到上面] 
 
 
 
只是为了解释为什么以上是不正确的（正如Riccardo所解释的），需要做的事情如下：
 
 
如果我们有一个文件NecessaryModule1.hs，如下所示：
   -  NecessaryModule1.hs 
模块NecessaryModule1其中
 
 addNumber1 :: Int  - > Int  - > Int 
 addNumber1 ab = a + b 
  
然后我们做：
 > ：load NecessaryModule1 
 [1的1]编译NecessaryModule1（必需的模块1.hs，解释）
好​​了，模块加载：必需模块1。 
> addNumber1 4 5 
 9 
> ：module -NecessaryModule1 
> addNumber1 4 5 
 
< interactive>：1：1：不在范围内：`addNumber1'
  
 
 <您必须使用ghci的命令才能加载数据库，而不是使用ghci命令来加载数据库。 （：module + My.Module ）和卸载（：module -My.Module ）已安装的模块。您也可以使用：m 而不是：module 来减少写入次数，如下所示：
  Prelude> ：m + Data.List 
 Prelude Data.List> sort [3,1,2] 
 [1,2,3] 
 Prelude Data.List> ：m -Data.List 
 Prelude> sort [3,1,2] 
 
< interactive>：1：1：不在范围内：`sort'
  
请记住，ghci提示符总是会提醒您当前已导入的模块：您可以查看该模块，以便知道使用：m -Module卸载的内容。 To.Unload 。
 
 
 
 特定文件  
 
 
如果您要加载的模块没有安装在系统中（例如，您编写了源代码并将其保存在某处），则需要使用其他命令：load filename.hs 。更快的方法是直接将路径作为 ghci 的命令行参数传递给文件，例如 ghci filename.hs 。如果您运行 winghci 并将其与 .hs 扩展名关联，则只需双击该文件即可。
 
 
 
在这两种情况下，您都会得到一个ghci提示符，指定的模块正确加载并在范围内导入（假设您没有得到编译错误）。与以前一样，现在可以使用：m [+/-] My.Module 来加载和卸载模块，但请注意，这与不同。 ：load 因为：module 假设你已经：load 进入/退出范围。
 
 
 
例如，如果您有 test.hs  
  module MyModule where 
 import Data.List 
 
fx = sort x 
  
您可以通过双击它（在带有winghci的windows上）来加载它，方法是输入 ghci test.hs ，或者加载 ghci 并键入：load test.hs （注意相对/绝对 
 
 
另一个有用的ghci命令是：reload ，它将重新编译你之前加载的模块。 
  Prelude>在您更改源文件时使用它，并且您想快速更新在ghci中加载的模块。 ：load test.hs 
 [1的1]编译MyModule（test.hs，解释）
好​​了，加载的模块：MyModule。 
 * MyModule> let xs = [1,2,3] in xs == f xs 
 True 
 * MyModule> ：重新加载$ ​​b $ b好​​了，加载的模块：MyModule。 
  
 ：help 会给你一个完整的列表所有可用的命令。
 
I loaded two modules (NecessaryModule1.hs and NecessaryModule2.hs as outlinked in Haskell : loading ALL files in current directory path). Now I want to unload NecessaryModule2.hs. I found an 'unload' function in System.Plugins.Load however but it did not work in WinGHCi. The error message I got was : 
>unload NecessaryModule2

<interactive>:1:1: Not in scope: `unload'

<interactive>:1:8:
    Not in scope: data constructor `NecessaryModule2'
I tried 
import System.Plugins.Load
but that did not work. Is there a way to unload modules in the manner described above?

---------------------------------------------------------------------------------------

[RESPONSE TO Riccardo]

Hi Riccardo, I tried your suggestion but I could not get it to work in WinGHCi. I had a file NecessaryModule1.hs as follows : 
module NecessaryModule1 where

addNumber1 :: Int -> Int -> Int
addNumber1 a b = a + b
I went to the location of the file via the ':cd' command, and then did : 
> :module +NecessaryModule1

<no location info>:
    Could not find module `NecessaryModule1':
      it is not a module in the current program, or in any known package.
Is this correct? Thanks [EDIT : see below for correction]

---------------------------------------------------------------------------------------

[CORRECTION TO ABOVE]

Just to explain why the above is incorrect (as explained by Riccardo), what needs to be done is the following :

If we have a file NecessaryModule1.hs as follows : 
--NecessaryModule1.hs
module NecessaryModule1 where

addNumber1 :: Int -> Int -> Int
addNumber1 a b = a + b
then we do : 
> :load NecessaryModule1
[1 of 1] Compiling NecessaryModule1 ( NecessaryModule1.hs, interpreted )
Ok, modules loaded: NecessaryModule1.
> addNumber1 4 5
9
> :module -NecessaryModule1
> addNumber1 4 5

<interactive>:1:1: Not in scope: `addNumber1'

解决方案
Installed modules

You have to use ghci's commands in order to load (:module +My.Module) and unload (:module -My.Module) installed modules. You can also use :m instead of :module in order to write less, like this:
Prelude> :m +Data.List
Prelude Data.List> sort [3,1,2]
[1,2,3]
Prelude Data.List> :m -Data.List
Prelude> sort [3,1,2]

<interactive>:1:1: Not in scope: `sort'
Remember that the ghci prompt always reminds you the module currently imported: you can have a look at that in  order to know what to unload with  :m -Module.To.Unload.

Specific files

If the module you're trying to load isn't installed in the system (e.g. you wrote the source and simply saved the file somewhere), you need to use a different command, :load filename.hs. A quicker way is to pass the path to the file directly as a command-line argument to ghci, e.g ghci filename.hs. If you run winghci and you associated it to the .hs extension, simply double-click the file.

In both cases you will get a ghci prompt with the specified module correctly loaded AND imported in scope (provided you don't have get compilation errors instead). As before, you can now use :m [+/-] My.Module to load and unload modules, but please note that this is different from :load because :module assumes you already :loaded what you're trying  to get in/out of scope.

E.g., if you have test.hs
module MyModule where
import Data.List

f x = sort x
you may load it by double-clicking it (on windows with winghci), by typing ghci test.hs in a console, or by loading ghci and typing :load test.hs (beware of relative/absolute paths).

Another useful ghci command is :reload, which will recompile the module you loaded before. Use it when you change the source file and you want to quickly update the module loaded in ghci.
Prelude> :load test.hs
[1 of 1] Compiling MyModule         ( test.hs, interpreted )
Ok, modules loaded: MyModule.
*MyModule> let xs = [1,2,3] in sort xs == f xs
True
*MyModule> :reload
Ok, modules loaded: MyModule.
:help will give you a complete list of all available commands.

                        
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