+(*
+ ||M|| This file is part of HELM, an Hypertextual, Electronic
+ ||A|| Library of Mathematics, developed at the Computer Science
+ ||T|| Department, University of Bologna, Italy.
+ ||I||
+ ||T|| HELM is free software; you can redistribute it and/or
+ ||A|| modify it under the terms of the GNU General Public License
+ \ / version 2 or (at your option) any later version.
+ \ / This software is distributed as is, NO WARRANTY.
+ V_______________________________________________________________ *)
+
+module U = NUri
+module C = Cps
+module L = Log
+module B = Brg
+module O = BrgOutput
+module E = BrgEnvironment
+module S = BrgSubstitution
+
+exception LRefNotFound of B.message
+
+type machine = {
+ c: B.context;
+ s: (B.term * int) list
+}
+
+(* Internal functions *******************************************************)
+
+let reductions = ref O.initial_reductions
+
+let level = 5
+
+let error i = raise (LRefNotFound (L.items1 (string_of_int i)))
+
+let log1 s c t =
+ let sc, st = s ^ " in the context", "the term" in
+ L.log O.specs level (L.ct_items1 sc c st t)
+
+let log2 s c u t =
+ let sc, su, st = s ^ " in the context", "the term", "and the term" in
+ L.log O.specs level (L.ct_items2 sc c su u st t)
+
+let empty_machine = {
+ c = B.empty_context; s = []
+}
+
+let get f c m i =
+ let f e = function
+ | Some (_, b) -> f e b
+ | None -> error i
+ in
+ let f c = B.get f c i in
+ B.append f c m.c
+
+let lift_stack f s =
+ let map f (v, i) = f (v, succ i) in
+ Cps.list_map f map s
+
+let unwind_to_term f m t =
+ let map f t (a, b) = f (B.Bind (a, b, t)) in
+ let f mc = C.list_fold_left f map t mc in
+ assert (m.s = []);
+ B.contents f m.c
+
+let push f m a b =
+ assert (m.s = []);
+ f {m with c = (a, b) :: m.c}
+
+(* to share *)
+let rec step f ?(delta=false) ?(sty=false) c m x =
+(* L.warn "entering R.step"; *)
+ match x with
+ | B.Sort _ -> f m x
+ | B.GRef (a, uri) ->
+ let f = function
+ | _, _, B.Abbr v when delta ->
+ reductions := O.add ~gdelta:1 !reductions;
+ step f ~delta ~sty c m v
+ | _, _, B.Abst w when sty ->
+ step f ~delta ~sty c m w
+ | e, _, b ->
+ f m (B.GRef (B.Entry (e, b) :: a, uri))
+ in
+ E.get_obj f uri
+ | B.LRef (a, i) ->
+ let f e = function
+ | B.Abbr v ->
+ reductions := O.add ~ldelta:1 !reductions;
+ step f ~delta ~sty c m v
+ | B.Abst w when sty ->
+ step f ~delta ~sty c m w
+ | b ->
+ f m (B.LRef (B.Entry (e, b) :: a, i))
+ in
+ let f e = S.lift_bind (f e) (succ i) (0) in
+ get f c m i
+ | B.Cast (_, _, t) ->
+ reductions := O.add ~tau:1 !reductions;
+ step f ~delta ~sty c m t
+ | B.Appl (_, v, t) ->
+ step f ~delta ~sty c {m with s = (v, 0) :: m.s} t
+ | B.Bind (a, B.Abst w, t) ->
+ begin match m.s with
+ | [] -> f m x
+ | (v, h) :: tl ->
+ reductions := O.add ~beta:1 !reductions;
+ let f mc = step f ~delta ~sty c {c = mc; s = tl} t in
+ let f v = B.push f m.c a (B.Abbr (B.Cast ([], w, v))) in
+ S.lift f h (0) v
+ end
+ | B.Bind (a, b, t) ->
+ reductions := O.add ~upsilon:(List.length m.s) !reductions;
+ let f sc mc = step f ~delta ~sty c {c = mc; s = sc} t in
+ let f sc = B.push (f sc) m.c a b in
+ lift_stack f m.s
+
+(* Interface functions ******************************************************)
+
+let domain f c t =
+ let f r = L.unbox level; f r in
+ let f m = function
+ | B.Bind (_, B.Abst w, _) ->
+ let f w = f (Some w) in unwind_to_term f m w
+ | x -> f None
+ in
+ L.box level; log1 "Now scanning" c t;
+ step f ~delta:true ~sty:true c empty_machine t
+
+let rec ac_nfs f ~si r c m1 u m2 t =
+(* L.warn "entering R.are_convertible_aux"; *)
+ log2 "Now converting nfs" c u t;
+ match u, t with
+ | B.Sort (_, h1), B.Sort (_, h2) ->
+ if h1 = h2 then f r else f false
+ | B.LRef (B.Entry (e1, B.Abst _) :: _, _),
+ B.LRef (B.Entry (e2, B.Abst _) :: _, _) ->
+ if e1 = e2 then ac_stacks f ~si r c m1 m2 else f false
+ | B.GRef (B.Entry (e1, B.Abst _) :: _, _),
+ B.GRef (B.Entry (e2, B.Abst _) :: _, _) ->
+ if e1 = e2 then ac_stacks f ~si r c m1 m2 else f false
+ | B.GRef (B.Entry (e1, B.Abbr v1) :: _, _),
+ B.GRef (B.Entry (e2, B.Abbr v2) :: _, _) ->
+ if e1 = e2 then
+ let f r =
+ if r then f r
+ else begin
+ reductions := O.add ~gdelta:2 !reductions;
+ ac f ~si true c m1 v1 m2 v2
+ end
+ in
+ ac_stacks f ~si r c m1 m2
+ else if e1 < e2 then begin
+ reductions := O.add ~gdelta:1 !reductions;
+ step (ac_nfs f ~si r c m1 u) c m2 v2
+ end else begin
+ reductions := O.add ~gdelta:1 !reductions;
+ step (ac_nfs_rev f ~si r c m2 t) c m1 v1
+ end
+ | _, B.GRef (B.Entry (_, B.Abbr v2) :: _, _) ->
+ reductions := O.add ~gdelta:1 !reductions;
+ step (ac_nfs f ~si r c m1 u) c m2 v2
+ | B.GRef (B.Entry (_, B.Abbr v1) :: _, _), _ ->
+ reductions := O.add ~gdelta:1 !reductions;
+ step (ac_nfs_rev f ~si r c m2 t) c m1 v1
+ | B.Bind (a1, (B.Abst w1 as b1), t1),
+ B.Bind (a2, (B.Abst w2 as b2), t2) ->
+ let g m1 m2 = ac f ~si r c m1 t1 m2 t2 in
+ let g m1 = push (g m1) m2 a2 b2 in
+ let f r = if r then push g m1 a1 b1 else f false in
+ ac f ~si r c m1 w1 m2 w2
+ | B.Sort _, B.Bind (a, b, t) when si ->
+ let f m1 m2 = ac f ~si r c m1 u m2 t in
+ let f m1 = push (f m1) m2 a b in
+ push f m1 a b
+ | _ -> f false
+
+and ac_nfs_rev f ~si r c m2 t m1 u = ac_nfs f ~si r c m1 u m2 t
+
+and ac f ~si r c m1 t1 m2 t2 =
+(* L.warn "entering R.are_convertible"; *)
+ let g m1 t1 = step (ac_nfs f ~si r c m1 t1) c m2 t2 in
+ if r = false then f false else step g c m1 t1
+
+and ac_stacks f ~si r c m1 m2 =
+(* L.warn "entering R.are_convertible_stacks"; *)
+ let mm1, mm2 = {m1 with s = []}, {m2 with s = []} in
+ let map f r (v1, h1) (v2, h2) =
+ let f v1 = S.lift (ac f ~si r c mm1 v1 mm2) h2 (0) v2 in
+ S.lift f h1 (0) v1
+ in
+ if List.length m1.s <> List.length m2.s then
+ begin
+(* L.warn (Printf.sprintf "Different lengths: %u %u"
+ (List.length m1.s) (List.length m2.s)
+ ); *)
+ f false
+ end
+ else
+ C.list_fold_left2 f map r m1.s m2.s
+
+let are_convertible f ?(si=false) c u t =
+ let f b = L.unbox level; f b in
+ L.box level; log2 "Now converting" c u t;
+ ac f ~si true c empty_machine u empty_machine t