定义模块VS.NET与F#Interactive [英] Defining Modules VS.NET vs F# Interactive

问题描述

我已经编写了这段代码，可以在VS.NET 2010中编译并完美运行

I have written this code which compiles and works perfectly in VS.NET 2010

module ConfigHandler
open System
open System.Xml
open System.Configuration

let GetConnectionString (key : string) =
  ConfigurationManager.ConnectionStrings.Item(key).ConnectionString

但是，当我进行控制+ A和Alt + Enter并将其发送给FSI时，我会收到错误消息

however when I do a control + A and Alt + Enter to send this to FSI I get an error

ConfigHandler.fs(2,1):错误FS0010:定义中的结构化构造意外启动.预期为"="或其他令牌.

ConfigHandler.fs(2,1): error FS0010: Unexpected start of structured construct in definition. Expected '=' or other token.

好.

所以我将代码更改为

module ConfigHandler =
  open System
  open System.Xml
  open System.Configuration

  let GetConnectionString (key : string) =
    ConfigurationManager.ConnectionStrings.Item(key).ConnectionString

现在Control + A，Alt + Enter成功，我的FSI很好地告诉了我

Now Control + A, Alt + Enter is successful and I FSI nicely tells me

模块ConfigHandler =开始 val GetConnectionString:字符串->字符串 结束

module ConfigHandler = begin val GetConnectionString : string -> string end

但是现在，如果我尝试在VS.NET 2010中编译代码，则会收到错误消息

However now If I try to compile my code in VS.NET 2010, I get an error message

库或多文件应用程序中的文件必须以名称空间或模块声明开头，例如'namespace SomeNamespace.SubNamespace'或'module SomeNamespace.SomeModule'

Files in libraries or multiple-file applications must begin with a namespace or module declaration, e.g. 'namespace SomeNamespace.SubNamespace' or 'module SomeNamespace.SomeModule'

我怎么都可以?是否可以在VS.NET中进行编译以及是否可以将模块发送到FSI?

How can I have both? Ability to compile in VS.NET and the ability to send modules to FSI?

推荐答案

这两个代码段之间存在微小但很关键的区别，这应该归咎于这里.

There is a tiny -- but crucial -- difference between your two snippets of code which is to blame here.

F#有两种声明module的方法.第一个是顶层模块"，其声明如下:

F# has two ways to declare a module. The first, a "top-level module", is declared like this:

module MyModule
// ... code goes here

声明模块的另一种方法是将其作为本地模块"，例如:

The other way to declare a module is as a "local module", like so:

module MyModule =
    // ... code goes here

顶级"和本地"声明之间的主要区别在于，本地声明后跟一个=符号，并且必须缩进本地"模块中的代码必须

The main differences between the "top-level" and "local" declarations are that the local declaration is followed by an = sign and the code within a "local" module must be indented.

第一个代码段收到ConfigHandler.fs(2,1): error FS0010: Unexpected start of structured construct in definition. Expected '=' or other token.消息的原因是，您无法在fsi中声明顶级模块.

The reason you get the ConfigHandler.fs(2,1): error FS0010: Unexpected start of structured construct in definition. Expected '=' or other token. message for the first snippet is that you can't declare top-level modules in fsi.

在模块定义中添加=符号后，它从顶级模块更改为本地模块.从那里，出现错误Files in libraries or multiple-file applications must begin with a namespace or module declaration, e.g. 'namespace SomeNamespace.SubNamespace' or 'module SomeNamespace.SomeModule'，因为本地模块必须嵌套在顶级模块或名称空间中. fsi不允许您定义名称空间(或顶级模块)，因此，如果要将整个文件复制粘贴到fsi中，唯一可行的方法是将编译指令用作@垫提到.否则，您可以简单地将本地模块定义(不包含名称空间)复制粘贴到fsi中，它们将按预期工作.

When you added the = sign to your module definition, it changed from a top-level module to a local module. From there, you got the error Files in libraries or multiple-file applications must begin with a namespace or module declaration, e.g. 'namespace SomeNamespace.SubNamespace' or 'module SomeNamespace.SomeModule' because local modules must be nested within a top-level module or a namespace. fsi doesn't allow you to define namespaces (or top-level modules), so if you want to copy-paste the entire file into fsi the only way it'll work is if you use the compilation directives as @pad mentioned. Otherwise, you can simply copy-paste the local module definitions (without the containing namespace) into fsi and they should work as expected.

参考: MSDN上的模块(F#)

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