在 F# 中将字节转换为枚举实例

发布于 2024-07-19 05:24:18 字数 348 浏览 1 评论 0原文

让我们考虑一下 C# 中的以下枚举

public enum ScrollMode : byte
{
      None = 0,
      Left = 1,
      Right = 2,
      Up = 3,
      Down = 4
}

F# 代码接收一个字节并且必须返回枚举的实例我已经尝试过

let mode = 1uy
let x = (ScrollMode)mode

（当然在实际应用程序中我无法设置“模式”，它作为网络数据的一部分被接收）。

上面的例子无法编译，有什么建议吗？

原文

Let's consider the following enum in C#

public enum ScrollMode : byte
{
      None = 0,
      Left = 1,
      Right = 2,
      Up = 3,
      Down = 4
}

The F# code receives a byte and has to return an instance of the enum
I have tried

let mode = 1uy
let x = (ScrollMode)mode

(Of course in the real application I do not get to set 'mode',
it is received as part of network data).

The example above does not compile, any suggestions?

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山川志 2024-07-26 05:24:18

对于基础类型为“int”的枚举，“enum”函数将执行转换，但对于非 int 枚举，您需要“LanguagePrimitives.EnumOfValue”，la：（

// define an enumerated type with an sbyte implementation
type EnumType =
  | Zero = 0y
  | Ten  = 10y

// examples to convert to and from
let x = sbyte EnumType.Zero
let y : EnumType = LanguagePrimitives.EnumOfValue 10y

这里列出了 EnumOfValue

http://research.microsoft. com/en-us/um/cambridge/projects/fsharp/manual/FSharp.Core/Microsoft.FSharp.Core.LanguagePrimitives.html

（现在 http://msdn.microsoft.com/en-us/library/ee340276(VS.100).aspx )

而此处列出了枚举

http://research.microsoft.com/en-us/um/cambridge/projects/fsharp/manual/FSharp.Core/Microsoft.FSharp.Core.Operators.html

（现在 http://msdn.microsoft.com/en-us/library/ee353754 (VS.100).aspx)
）

For enums whose underlying type is 'int', the 'enum' function will do the conversion, but for non-int enums, you need 'LanguagePrimitives.EnumOfValue', a la:

// define an enumerated type with an sbyte implementation
type EnumType =
  | Zero = 0y
  | Ten  = 10y

// examples to convert to and from
let x = sbyte EnumType.Zero
let y : EnumType = LanguagePrimitives.EnumOfValue 10y

(EnumOfValue is listed here

http://research.microsoft.com/en-us/um/cambridge/projects/fsharp/manual/FSharp.Core/Microsoft.FSharp.Core.LanguagePrimitives.html

(now http://msdn.microsoft.com/en-us/library/ee340276(VS.100).aspx )

whereas enum is listed here

http://research.microsoft.com/en-us/um/cambridge/projects/fsharp/manual/FSharp.Core/Microsoft.FSharp.Core.Operators.html

(now http://msdn.microsoft.com/en-us/library/ee353754(VS.100).aspx )
)

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