CS334 ML Command Line Options Cheat Sheet

ML programs can process command line arguments, provided you structure them in the following way. You may find this handy if, for example, you would like to write a script to generate many different random art pictures. The following example program shows how to access the command line:

  (* command.sml *)

  (* get the arguments *)
  let val l = CommandLine.arguments() in

    (* print them *)
    map (fn x => (print x; print "\n")) l;

    (* exit from the interpreter.  Always include
       this as the last line of your code. *)
    OS.Process.exit OS.Process.success : unit

  end;

Running

  sml command.sml a b c

will print

  Standard ML of New Jersey v110.60 [built: Tue Feb 19 11:44:38 2008]
  [opening command.sml]
  [autoloading]
  [library $SMLNJ-BASIS/basis.cm is stable]
  [autoloading done]
  command.sml 
  a
  b
  c

Here's another handy code snippet that converts a string to an integer:

  - fun stringToInt s = 
      case Int.fromString(s) of
         NONE    => raise Fail("Bad Number " ^ s)
       | SOME(n) => n;

  - stringToInt "3";
  val it = 3: int
  - stringToInt "-23";
  val it = ~23;
  - stringToInt "cow";
  uncaught exception Fail [Fail: Bad Number: cow]