## Flag options

`val store_const : ?default:'a -> 'a -> 'a Opt.t`

`store_const ?default const` returns a flag option which stores the constant value `const` when the option is encountered on the command line.

`val store_true : unit -> bool Opt.t`

`store_true ()` returns an option which is set to true when it is encountered on the command line. The default value is false.

`val store_false : unit -> bool Opt.t`

`store_false ()` returns an option which is set to false when it is encountered on the command line. The default value is true.

`val count_option : ?dest:int Stdlib.ref -> ?increment:int -> unit -> int Opt.t`

Create a counting option which increments its value each time the option is encountered on the command line.

- parameter increment

  Increment to add to the option value each time the option is encountered.

- parameter dest

  Reference to the option value. Useful for making options like '--quiet' and '--verbose' sharing a single value.

- returns

  the newly created option.

`val incr_option : ?dest:int Stdlib.ref -> unit -> int Opt.t`

Exactly identical to `count_option ~dest:dest ~increment:1 ()`.

`val decr_option : ?dest:int Stdlib.ref -> unit -> int Opt.t`

Exactly identical to `count_option ~dest:dest ~increment:(-1) ()`.

## Value options

`val int_option : ?default:int -> ?metavar:string -> unit -> int Opt.t`

`int_option ?default ?metavar ()` returns an option which takes a single integer argument. If `~default` is given it is the default value returned when the option has not been encountered on the command line.

`val float_option : ?default:float -> ?metavar:string -> unit -> float Opt.t`

See `OptParse.StdOpt.int_option`.

`val str_option : ?default:string -> ?metavar:string -> unit -> string Opt.t`

See `OptParse.StdOpt.int_option`.

`val any_option : ?default:'a option -> ?metavar:string -> (string -> 'a) -> 'a Opt.t`

`any_option ?default ?metavar coerce` returns an option which takes a single argument from the command line and calls `coerce` to coerce it to the proper type.

`default` is the default value of the option. If `None`, the option has no default value.

## Callback options

`val int_callback : ?metavar:string -> (int -> unit) -> unit Opt.t`

`int_callback ?metavar f` returns an option which takes a single integer argument and calls `f` with that argument when encountered on the command line.

`val float_callback : ?metavar:string -> (float -> unit) -> unit Opt.t`

See `OptParse.StdOpt.int_callback`.

`val str_callback : ?metavar:string -> (string -> unit) -> unit Opt.t`

See `OptParse.StdOpt.int_callback`.

## Special options

`val help_option : unit -> 'a Opt.t`

`help_option ()` returns the standard help option which displays a usage message and exits the program when encountered on the command line.

`val version_option : (unit -> string) -> 'a Opt.t`

`version_option f` returns the standard version option which displays the string returned by `f ()` (and nothing else) on standard output and exits.