let rulesText = """
00*1 ADD
01*1 SUB
10*1 MUL
"""

type conv = System.Convert

let mask (s : string) = conv.ToInt32 (s.Replace('1', '0').Replace('*', '1'), 2) |> (~~~)

let bits (s : string) = conv.ToInt32 (s.Replace('*', '0'), 2) 

let ops (rules : string) = 
        let result = Array.create 16 "-"
        for e in rulesText.Trim().Split('\n') do
                let xy      = e.Split() 
                let m, b, x = mask xy.[0], bits xy.[0], xy.[1]
                for i in 0..result.Length-1 do 
                        if i &&& m = b then result.[i] <- x 
        result

do 
    ops rulesText 
    |> Array.iteri (fun i e -> printfn "%s %s" (conv.ToString(i, 2).PadLeft(4, '0')) e)