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(***********************************************************************)
(* *)
(* Objective Caml *)
(* *)
(* Damien Doligez, projet Para, INRIA Rocquencourt *)
(* *)
(* Copyright 1996 Institut National de Recherche en Informatique et *)
(* en Automatique. All rights reserved. This file is distributed *)
(* under the terms of the GNU Library General Public License, with *)
(* the special exception on linking described in file ../LICENSE. *)
(* *)
(***********************************************************************)

(* $Id$ *)

(** Parsing of command line arguments.

This module provides a general mechanism for extracting options and
arguments from the command line to the program.

Syntax of command lines:
A keyword is a character string starting with a [-].
An option is a keyword alone or followed by an argument.
The types of keywords are: [Unit], [Bool], [Set], [Clear],
[String], [Set_string], [Int], [Set_int], [Float], [Set_float],
[Tuple], [Symbol], and [Rest].
[Unit], [Set] and [Clear] keywords take no argument. A [Rest]
keyword takes the remaining of the command line as arguments.
Every other keyword takes the following word on the command line
as argument.
Arguments not preceded by a keyword are called anonymous arguments.

Examples ([cmd] is assumed to be the command name):
- [cmd -flag ](a unit option)
- [cmd -int 1 ](an int option with argument [1])
- [cmd -string foobar ](a string option with argument ["foobar"])
- [cmd -float 12.34 ](a float option with argument [12.34])
- [cmd a b c ](three anonymous arguments: ["a"], ["b"], and ["c"])
- [cmd a b -- c d ](two anonymous arguments and a rest option with
two arguments)
*)

type spec =
  | Unit of (unit -> unit) (** Call the function with unit argument *)
  | Bool of (bool -> unit) (** Call the function with a bool argument *)
  | Set of bool ref (** Set the reference to true *)
  | Clear of bool ref (** Set the reference to false *)
  | String of (string -> unit) (** Call the function with a string argument *)
  | Set_string of string ref (** Set the reference to the string argument *)
  | Int of (int -> unit) (** Call the function with an int argument *)
  | Set_int of int ref (** Set the reference to the int argument *)
  | Float of (float -> unit) (** Call the function with a float argument *)
  | Set_float of float ref (** Set the reference to the float argument *)
  | Tuple of spec list (** Take several arguments according to the
spec list *)
  | Symbol of string list * (string -> unit)
                               (** Take one of the symbols as argument and
call the function with the symbol *)
  | Rest of (string -> unit) (** Stop interpreting keywords and call the
function with each remaining argument *)
(** The concrete type describing the behavior associated
with a keyword. *)

type key = string
type doc = string
type usage_msg = string
type anon_fun = (string -> unit)

val parse :
  (key * spec * doc) list -> anon_fun -> usage_msg -> unit
(** [Arg.parse speclist anon_fun usage_msg] parses the command line.
[speclist] is a list of triples [(key, spec, doc)].
[key] is the option keyword, it must start with a ['-'] character.
[spec] gives the option type and the function to call when this option
is found on the command line.
[doc] is a one-line description of this option.
[anon_fun] is called on anonymous arguments.
The functions in [spec] and [anon_fun] are called in the same order
as their arguments appear on the command line.

If an error occurs, [Arg.parse] exits the program, after printing
to standard error an error message as follows:
- The reason for the error: unknown option, invalid or missing argument, etc.
- [usage_msg]
- The list of options, each followed by the corresponding [doc] string.

For the user to be able to specify anonymous arguments starting with a
[-], include for example [("-", String anon_fun, doc)] in [speclist].

By default, [parse] recognizes two unit options, [-help] and [--help],
which will print to standard output [usage_msg] and the list of
options, and exit the program. You can override this behaviour
by specifying your own [-help] and [--help] options in [speclist].
*)

val parse_argv : ?current: int ref -> string array ->
  (key * spec * doc) list -> anon_fun -> usage_msg -> unit
(** [Arg.parse_argv ~current args speclist anon_fun usage_msg] parses
the array [args] as if it were the command line. It uses and updates
the value of [~current] (if given), or [Arg.current]. You must set
it before calling [parse_argv]. The initial value of [current]
is the index of the program name (argument 0) in the array.
If an error occurs, [Arg.parse_argv] raises [Arg.Bad] with
the error message as argument. If option [-help] or [--help] is
given, [Arg.parse_argv] raises [Arg.Help] with the help message
as argument.
*)

exception Help of string
(** Raised by [Arg.parse_argv] when the user asks for help. *)

exception Bad of string
(** Functions in [spec] or [anon_fun] can raise [Arg.Bad] with an error
message to reject invalid arguments.
[Arg.Bad] is also raised by [Arg.parse_argv] in case of an error. *)

val usage : (key * spec * doc) list -> usage_msg -> unit
(** [Arg.usage speclist usage_msg] prints to standard error
an error message that includes the list of valid options. This is
the same message that {!Arg.parse} prints in case of error.
[speclist] and [usage_msg] are the same as for [Arg.parse]. *)

val usage_string : (key * spec * doc) list -> usage_msg -> string
(** Returns the message that would have been printed by {!Arg.usage},
if provided with the same parameters. *)

val align: (key * spec * doc) list -> (key * spec * doc) list;;
(** Align the documentation strings by inserting spaces at the first
space, according to the length of the keyword. Use a
space as the first character in a doc string if you want to
align the whole string. The doc strings corresponding to
[Symbol] arguments are aligned on the next line. *)

val current : int ref
(** Position (in {!Sys.argv}) of the argument being processed. You can
change this value, e.g. to force {!Arg.parse} to skip some arguments.
{!Arg.parse} uses the initial value of {!Arg.current} as the index of
argument 0 (the program name) and starts parsing arguments
at the next element. *)
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