確保計算中的一致單位

度量單位是可以新增到浮點數或整數的附加型別註釋。它們可用於在編譯時驗證計算是否始終使用單位。

要定義註釋：

[<Measure>] type m // meters
[<Measure>] type s // seconds
[<Measure>] type accel = m/s^2 // acceleration defined as meters per second squared

定義後，註釋可用於驗證表示式是否產生預期型別。

// Compile-time checking that this function will return meters, since (m/s^2) * (s^2) -> m
// Therefore we know units were used properly in the calculation.
let freeFallDistance (time:float<s>) : float<m> = 
    0.5 * 9.8<accel> * (time*time)    

// It is also made explicit at the call site, so we know that the parameter passed should be in seconds
let dist:float<m> = freeFallDistance 3.0<s>
printfn "%f" dist