1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
(************************************************************************) (* * The Coq Proof Assistant / The Coq Development Team *) (* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) (* <O___,, * (see CREDITS file for the list of authors) *) (* \VV/ **************************************************************) (* // * This file is distributed under the terms of the *) (* * GNU Lesser General Public License Version 2.1 *) (* * (see LICENSE file for the text of the license) *) (************************************************************************) type 'a content = | Unset | Default of 'a | Set of 'a type 'a t = 'a content ref type 'a value = 'a t let get (hook : 'a value) = match !hook with | Unset -> assert false | Default data | Set data -> data let set (hook : 'a t) data = match !hook with | Unset | Default _ -> hook := Set data | Set _ -> assert false let make ?default () = let data = match default with | None -> Unset | Some data -> Default data in let ans = ref data in (ans, ans)