是否可以通过显式或隐式转换来定义kB，GB，...的度量单位? [英] Is it possible to define units of measure for kB, GB, ... with explicit or implicit conversion?

问题描述

我想定义一个度量类型

[<Measure>] type kB

可在显式转换为int时转换为字节数:

that converts to the number of bytes when explicitly cast to an int:

(int)7<kB>   // would result 1024kB - explicit would be fine

由于无法将显式转换运算符添加到C#中的类型，因此我陷入了困境.有人有主意吗? 甚至更好的是隐式转换，这样，当一个函数需要一定数量的字节时，可以像

Since there is no way to add an explicit conversion operator to a type like in C#, I am stuck. Anyone has an idea? Even better would be an implicit conversion, so that when a function requires numbers of bytes, it can be called like

Allocate(7<kB>) // implicit would be superfine

特殊的转换函数没有吸引力-编写kB函数很简单，但效果却不那么好:

Special conversion functions do not appeal - writing a kB function is trivial but not as nice:

let kB(n) = 1024 * n
kB(7)
7 |> kB

与单位功能相同的转换函数也不酷

A conversion function that does the same with units is not cool either

7<kB> |> convertToByte

推荐答案

活动模式对您来说足够酷"吗?

Are active patterns "cool" enough for you?

[<Measure>] type kB

// single case active pattern to convert from kB to raw B value
let (|Bytes|) (x : int<kB>) = int(x * 1024)

// use pattern matching in the declaration
// val printBytes : int<kB> -> unit
let printBytes (Bytes(b)) = 
    printfn "It's %d bytes" b

printBytes 7<kB>
// "It's 7168 bytes"

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