Преобразование 10-го целого в двоичное представление

open System

let bin x =
    
    let rec b a x =
        let o = x % 2
        let d = x / 2
        let r =
            match o with
            | 1 -> "1" + a
            | 0 -> "0" + a
        if d > 0 then b r d  else r

    b "" x

type Int32 with
    member it.ToBin () =
        bin it

[<STAThread>]
[<EntryPoint>]
let main _ =
    let i = 0b101
    printfn "%s" (i.ToBin())
    exit 0