Why wont this .sml file load correctly into my enviorment without getting a bunch of errors????

(*strip: function that inputs two file names, one for reading and one for writing, and removes non-integers from the input file, writing the result to the output file*)

fun strip (inputFile:string) (outputFile:string) : unit =

let input = TextIO.openIn inputFile in

let output = TextIO.openOut outputFile in

let rec processLine () =

let line = TextIO.inputLine input in

match line with

| None -> TextIO.closeIn input; TextIO.closeOut output

| Some s ->

match Int.fromString s with

| Some i -> TextIO.outputLine output (Int.toString i); processLine()

| None -> processLine()

processLine()