Standard ML
programs are often used in interactive shells(?) However, we can not only use it in an interactive shell, but also compile it to create executable commands.
To get a command name and arguments
In Standard ML
, CommandLine
structure provides name
function and arguments
. Command names and command line arguments will be obtained by them.
name
function
— CommandLine.name;
val it = fn: unit -> string
CommandLine.name ()
yields the command name as a string.
arguments
function
- CommandLine.arguments;
val it = fn: unit -> string list
CommandLine.arguments ()
gives command line arguments as a list of string types.
Termination process
To close the program and return to the shell, use the Process.exit
function of OS
structure.
- OS.Process.exit
val it = OS.Process.status -> 'a
The argument OS.Process.status
is an exit status data type to pass to the shell. There are two types:
-
OS.Process.success
: Success (Corresponds toEXIT_SUCCESS
in C) -
OS.Process.failure
: Failure (Corresponds toEXIT_FAILURE
in C)
To run a program
val arg = someFunc1
val _ = (someFunc2 arg; ...)
You can execute defined functions by evaluating them at the top level. The return value of functions should be discarded using an underscore or serial execution if they only use side effects.
Example
If you compile it with mlton
, it becomes an executable.
(* someCommand.sml *)
val n = ref 0
fun prName () = print ("Name: \n" ^ CommandLine.name () ^ " \n")
fun prArg () = foldl (fn (z, unt) => print ((n := !n + 1; Int.toString (!n)) ^ ":" ^ z ^ " \n")) (print "Arguments: \n") (CommandLine.arguments ())
val _ = (prName (); prArg (); OS.Process.exit (OS.Process.success))
$ mlton someCommand.sml
$ ./someCommand a b c d
Name:
./someCommand
Arguments:
1: a
2: b
3: c
4: d
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