fun count file =
    let open TextIO
        val is = openIn file
        fun loop res = if endOfStream is then res 
                       else (inputLine is; loop (res+1))
    in loop 0 before closeIn is end

val files = List.filter (fn p => Path.ext p = SOME "sml" 
                                 orelse Path.ext p = SOME "sig") 
                        (Mosml.listDir ".")

val lines = List.foldl (op +) 0 (map count files)