Parse command-line arguments: Difference between revisions

=={{header|Standard ML}}==

{{works with|SML/NJ}}

{{works with|MLton}}

The following code listing can be compiled with both [[SML/NJ]] and [[MLton]]:

<lang sml>structure Test = struct

exception FatalError of string

fun main (prog, args) =

(let

exception Args

val switch = ref false

fun do_A arg = print ("Argument of -A is " ^ arg ^ "\n")

fun do_B () = if !switch then print "switch is on\n" else print "switch is off\n"

fun usage () = print ("Usage: " ^ prog ^ " [-help] [-switch] [-A Argument] [-B]\n")

fun parseArgs nil = ()

| parseArgs ("-help" :: ts) = (usage(); parseArgs ts)

| parseArgs ("-switch" :: ts) = (switch := true; parseArgs ts)

| parseArgs ("-A" :: arg :: ts) = (do_A arg; parseArgs ts)

| parseArgs ("-B" :: ts) = (do_B(); parseArgs ts)

| parseArgs _ = (usage(); raise Args)

in

parseArgs args handle Args => raise FatalError "Error parsing args. Use the -help option.";

(* Do something; *)

OS.Process.success

end)

handle FatalError e => (print ("Fatal Error:\n"^e^"\n"); OS.Process.failure)

end

(* MLton *)

val _ = Test.main (CommandLine.name(), CommandLine.arguments())</lang>

=== SML/NJ ===

[[SML/NJ]] can compile source code to a "heap file", witch can than be executed by the interpreter with arguments given (see [http://stackoverflow.com/questions/5053149/sml-nj-how-to-compile-standalone-executable this entry on stackowerflow.com] for more information).

The <code>source.cm</code> file should lock like this:

<lang>Group

is

SOURCE_FILE.sml

$/basis.cm</lang>

To compile the program, use <code>ml-build sources.cm</code>. This should create a "heap file" <code>sources.x86-linux</code>, depending on your architecture.

The heap file can be executed with <code>sml @SMLload=sources.x86-linux ARGUMENTS</code>, or the script [http://www.smlnj.org/doc/heap2exec/index.html <code>heap2exec</code>] can be used to make a single executable.

=== MLton ===

[[MLton]] compiles the source file directly to a executable by invoking <code>mlton SOURCE_FILE.sml</code>.