56 lines
1.8 KiB
OCaml
56 lines
1.8 KiB
OCaml
(* Copyright (C) 2017--2024 Petter A. Urkedal <paurkedal@gmail.com>
|
|
*
|
|
* This library is free software; you can redistribute it and/or modify it
|
|
* under the terms of the GNU Lesser General Public License as published by
|
|
* the Free Software Foundation, either version 3 of the License, or (at your
|
|
* option) any later version, with the LGPL-3.0 Linking Exception.
|
|
*
|
|
* This library is distributed in the hope that it will be useful, but WITHOUT
|
|
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
|
|
* License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public License
|
|
* and the LGPL-3.0 Linking Exception along with this library. If not, see
|
|
* <http://www.gnu.org/licenses/> and <https://spdx.org>, respectively.
|
|
*)
|
|
|
|
(** Multiplicities of zero, one, and many. *)
|
|
|
|
type +'m t = (* not GADT due to variance *)
|
|
| Zero
|
|
| One
|
|
| Zero_or_one
|
|
| Zero_or_more
|
|
constraint 'm = [< `Zero | `One | `Many]
|
|
|
|
type zero = [`Zero]
|
|
type one = [`One]
|
|
type zero_or_one = [`Zero | `One]
|
|
type zero_or_more = [`Zero | `One | `Many]
|
|
|
|
let zero : [> `Zero] t = Zero
|
|
let one : [> `One] t = One
|
|
let zero_or_one : [> `Zero | `One] t = Zero_or_one
|
|
let zero_or_more : ([> `Zero | `One | `Many] as 'a) t = Zero_or_more
|
|
|
|
let only_zero : [< `Zero] t -> unit =
|
|
function Zero -> () | _ -> assert false
|
|
let only_one : [< `One] t -> unit =
|
|
function One -> () | _ -> assert false
|
|
let only_zero_or_one : [< `Zero | `One] t -> unit =
|
|
function Zero | One -> () | _ -> assert false
|
|
|
|
let expose = function
|
|
| Zero -> `Zero
|
|
| One -> `One
|
|
| Zero_or_one -> `Zero_or_one
|
|
| Zero_or_more -> `Zero_or_more
|
|
|
|
let can_be_zero = function
|
|
| One -> false
|
|
| Zero | Zero_or_one | Zero_or_more -> true
|
|
|
|
let can_be_many = function
|
|
| Zero | One | Zero_or_one -> false
|
|
| Zero_or_more -> true
|