cross-product.sml

fun readLine () = TextIO.inputLine TextIO.stdIn
fun writeLine str = TextIO.outputSubstr (TextIO.stdOut, Substring.full str)

fun main () =
  let
    val words = String.tokens (fn x => x = #" ")

    fun input keys vals =
      case readLine () of
        SOME(line) => (
          case words line of
            (k :: v :: _) =>
              input (k :: keys) (v :: vals)
        )
      | NONE =>
          (keys, vals)
    
    val (keys, vals) = input [] []
  in
    List.app (fn k => List.app (fn v => writeLine (k ^ " " ^ v)) (List.rev vals)) (List.rev keys)
  end

val _ = main()