1: type AccountState = 
 2:     | Overdrawn
 3:     | Silver
 4:     | Gold
 5: [<Measure>] type USD
 6: type Account<[<Measure>] 'u>() =
 7:     let mutable balance = 0.0<_>   
 8:     member this.State
 9:         with get() = 
10:             match balance with
11:             | _ when balance <= 0.0<_> -> Overdrawn
12:             | _ when balance > 0.0<_> && balance < 10000.0<_> -> Silver
13:             | _ -> Gold
14:     member this.PayInterest() = 
15:         let interest = 
16:             match this.State with
17:                 | Overdrawn -> 0.
18:                 | Silver -> 0.01
19:                 | Gold -> 0.02
20:         interest * balance
21:     member this.Deposit(x:float<_>) =  
22:         let (a:float<_>) = x
23:         balance <- balance + a
24:     member this.Withdraw(x:float<_>) = balance <- balance - x
25: 
26: let state() = 
27:     let account = Account()
28: 
29:     account.Deposit(10000.<USD>)
30:     printfn "interest = %A" (account.PayInterest())
31: 
32:     account.Withdraw(20000.<USD>)
33:     printfn "interest = %A" (account.PayInterest())
34: