2 ||M|| This file is part of HELM, an Hypertextual, Electronic
3 ||A|| Library of Mathematics, developed at the Computer Science
4 ||T|| Department, University of Bologna, Italy.
6 ||T|| HELM is free software; you can redistribute it and/or
7 ||A|| modify it under the terms of the GNU General Public License
8 \ / version 2 or (at your option) any later version.
9 \ / This software is distributed as is, NO WARRANTY.
10 V_______________________________________________________________ *)
15 type bind = Void (* exclusion *)
16 | Abst of term (* abstraction *)
17 | Abbr of term (* abbreviation *)
19 and term = Sort of int (* hierarchy index *)
20 | LRef of int (* reverse de Bruijn index *)
21 | GRef of uri (* reference *)
22 | Cast of term * term (* type, term *)
23 | Appl of term * term (* argument, function *)
24 | Bind of id * bind * term (* name, binder, scope *)
26 type obj = int * uri * bind (* age, uri, binder, contents *)
28 type item = obj option
30 type context = int * (id * bind) list
32 type message = (context, term) Log.item list
34 type hierarchy = int -> int
36 (* Currified constructors ***************************************************)
42 let cast u t = Cast (u, t)
44 let appl u t = Appl (u, t)
46 let bind id b t = Bind (id, b, t)
48 (* context handling functions ***********************************************)
50 let empty_context = 0, []
52 let push f (l, es) id b =
53 let c = succ l, (id, b) :: es in
56 let append f (l1, es1) (l2, es2) =
57 f (l2 + l1, List.append es2 es1)
59 let map f map (l, es) =
60 let f es = f (l, es) in
63 let contents f (l, es) = f l es
66 if i < 0 || i >= l then f None else
67 let result = List.nth es (l - succ i) in