module NonNegativeInt = 

  type T = private | NonNegativeInt of int

  let mutable saved:int = 0

  let create i = 

    if (i >= 0 )

    then 

        saved  <- i

        Some (NonNegativeInt i)

    else None

  let get = 

      2

open NonNegativeInt

​

module Test =

  let show (input:T option) =

     match input with

     | Some i -> 

        printfn "%i" ( 10*NonNegativeInt.get) 

open Test

​

show (NonNegativeInt.create -42)

​