* http://cs.unibo.it/helm/.
*)
+let _profiler = <:profiler<_profiler>>;;
+
(* $Id: inference.ml 6245 2006-04-05 12:07:51Z tassi $ *)
type rule = SuperpositionRight | SuperpositionLeft | Demodulation
and goal_proof = (rule * Utils.pos * int * Subst.substitution * Cic.term) list
;;
+type goal = goal_proof * Cic.metasenv * Cic.term
+
(* globals *)
let maxid = ref 0;;
let id_to_eq = Hashtbl.create 1024;;
let id = freshid () in
let eq = (uncomparable,weight,p,(ty,l,r,o),m,id) in
Hashtbl.add id_to_eq id eq;
+
eq
;;
Pervasives.compare s1 s2
;;
+let rec max_weight_in_proof current =
+ function
+ | Exact _ -> current
+ | Step (_, (_,id1,(_,id2),_)) ->
+ let eq1 = Hashtbl.find id_to_eq id1 in
+ let eq2 = Hashtbl.find id_to_eq id2 in
+ let (w1,p1,(_,_,_,_),_,_) = open_equality eq1 in
+ let (w2,p2,(_,_,_,_),_,_) = open_equality eq2 in
+ let current = max current w1 in
+ let current = max_weight_in_proof current p1 in
+ let current = max current w2 in
+ max_weight_in_proof current p2
+
+let max_weight_in_goal_proof =
+ List.fold_left
+ (fun current (_,_,id,_,_) ->
+ let eq = Hashtbl.find id_to_eq id in
+ let (w,p,(_,_,_,_),_,_) = open_equality eq in
+ let current = max current w in
+ max_weight_in_proof current p)
+
+let max_weight goal_proof proof =
+ let current = max_weight_in_proof 0 proof in
+ max_weight_in_goal_proof current goal_proof
+
let proof_of_id id =
try
let (_,p,(_,l,r,_),_,_) = open_equality (Hashtbl.find id_to_eq id) in
let open_pred pred =
match pred with
- | Cic.Lambda (_,ty,(Cic.Appl [Cic.MutInd (uri, 0,_);_;l;r]))
+ | Cic.Lambda (_,_,(Cic.Appl [Cic.MutInd (uri, 0,_);ty;l;r]))
when LibraryObjects.is_eq_URI uri -> ty,uri,l,r
| _ -> prerr_endline (CicPp.ppterm pred); assert false
;;
CicSubstitution.subst (Cic.Rel 1) t
;;
+let head_of_apply = function | Cic.Appl (hd::_) -> hd | t -> t;;
+let tail_of_apply = function | Cic.Appl (_::tl) -> tl | t -> [];;
+let count_args t = List.length (tail_of_apply t);;
+let rec build_nat =
+ let u = UriManager.uri_of_string "cic:/matita/nat/nat/nat.ind" in
+ function
+ | 0 -> Cic.MutConstruct(u,0,1,[])
+ | n ->
+ Cic.Appl [Cic.MutConstruct(u,0,2,[]);build_nat (n-1)]
+;;
+let tyof context menv t =
+ try
+ fst(CicTypeChecker.type_of_aux' menv context t CicUniv.empty_ugraph)
+ with
+ | CicTypeChecker.TypeCheckerFailure _
+ | CicTypeChecker.AssertFailure _ -> assert false
+;;
+let rec lambdaof left context = function
+ | Cic.Prod (n,s,t) ->
+ Cic.Lambda (n,s,lambdaof left context t)
+ | Cic.Appl [Cic.MutInd (uri, 0,_);ty;l;r]
+ when LibraryObjects.is_eq_URI uri -> if left then l else r
+ | t ->
+ let names = Utils.names_of_context context in
+ prerr_endline ("lambdaof: " ^ (CicPp.pp t names));
+ assert false
+;;
-let canonical t =
+let canonical t context menv =
let rec remove_refl t =
match t with
| Cic.Appl (((Cic.Const(uri_trans,ens))::tl) as args)
Cic.LetIn (name,remove_refl bo,remove_refl rest)
| _ -> t
in
- let rec canonical t =
+ let rec canonical context t =
match t with
- | Cic.LetIn(name,bo,rest) -> Cic.LetIn(name,canonical bo,canonical rest)
+ | Cic.LetIn(name,bo,rest) ->
+ let context' = (Some (name,Cic.Def (bo,None)))::context in
+ Cic.LetIn(name,canonical context bo,canonical context' rest)
| Cic.Appl (((Cic.Const(uri_sym,ens))::tl) as args)
when LibraryObjects.is_sym_eq_URI uri_sym ->
(match p_of_sym ens tl with
| Cic.Appl ((Cic.Const(uri,ens))::tl)
when LibraryObjects.is_sym_eq_URI uri ->
- canonical (p_of_sym ens tl)
+ canonical context (p_of_sym ens tl)
| Cic.Appl ((Cic.Const(uri_trans,ens))::tl)
when LibraryObjects.is_trans_eq_URI uri_trans ->
let ty,l,m,r,p1,p2 = open_trans ens tl in
mk_trans uri_trans ty r m l
- (canonical (mk_sym uri_sym ty m r p2))
- (canonical (mk_sym uri_sym ty l m p1))
+ (canonical context (mk_sym uri_sym ty m r p2))
+ (canonical context (mk_sym uri_sym ty l m p1))
+ | Cic.Appl (([Cic.Const(uri_feq,ens);ty1;ty2;f;x;y;p])) ->
+
+ let eq_f_sym =
+ Cic.Const (UriManager.uri_of_string
+ "cic:/matita/logic/equality/eq_f1.con",[])
+ in
+ Cic.Appl (([eq_f_sym;ty1;ty2;f;x;y;p]))
+
+(*
+ let sym_eq = Cic.Const(uri_sym,ens) in
+ let eq_f = Cic.Const(uri_feq,[]) in
+ let b = Cic.MutConstruct (UriManager.uri_of_string
+ "cic:/matita/datatypes/bool/bool.ind",0,1,[])
+ in
+ let u = ty1 in
+ let ctx = f in
+ let n = build_nat (count_args p) in
+ let h = head_of_apply p in
+ let predl = lambdaof true context (tyof context menv h) in
+ let predr = lambdaof false context (tyof context menv h) in
+ let args = tail_of_apply p in
+ let appl =
+ Cic.Appl
+ ([Cic.Const(UriManager.uri_of_string
+ "cic:/matita/paramodulation/rewrite.con",[]);
+ eq; sym_eq; eq_f; b; u; ctx; n; predl; predr; h] @
+ args)
+ in
+ appl
+*)
+(*
| Cic.Appl (((Cic.Const(uri_ind,ens)) as he)::tl)
when LibraryObjects.is_eq_ind_URI uri_ind ||
LibraryObjects.is_eq_ind_r_URI uri_ind ->
Cic.Appl
[he;ty;what;pred;
canonical (mk_sym uri_sym ty l r p1);other;canonical p2]
+*)
| Cic.Appl [Cic.MutConstruct (uri, 0, 1,_);_;_] as t
when LibraryObjects.is_eq_URI uri -> t
- | _ -> Cic.Appl (List.map canonical args))
- | Cic.Appl l -> Cic.Appl (List.map canonical l)
+ | _ -> Cic.Appl (List.map (canonical context) args))
+ | Cic.Appl l -> Cic.Appl (List.map (canonical context) l)
| _ -> t
in
- remove_refl (canonical t)
+ remove_refl (canonical context t)
;;
let ty_of_lambda = function
| _ -> assert false
;;
+let mk_feq uri_feq ty ty1 left pred right t =
+ Cic.Appl [Cic.Const(uri_feq,[]);ty;ty1;pred;left;right;t]
+;;
+
let contextualize uri ty left right t =
let hole = Cic.Implicit (Some `Hole) in
(* aux [uri] [ty] [left] [right] [ctx] [t]
* that is used only by the base case
*
* ctx is a term with an hole. Cic.Implicit(Some `Hole) is the empty context
+ * ty_ctx is the type of ctx_d
*)
- let rec aux uri ty left right ctx_d = function
+ let rec aux uri ty left right ctx_d ctx_ty = function
| Cic.Appl ((Cic.Const(uri_sym,ens))::tl)
when LibraryObjects.is_sym_eq_URI uri_sym ->
let ty,l,r,p = open_sym ens tl in
- mk_sym uri_sym ty l r (aux uri ty l r ctx_d p)
+ mk_sym uri_sym ty l r (aux uri ty l r ctx_d ctx_ty p)
| Cic.LetIn (name,body,rest) ->
(* we should go in body *)
- Cic.LetIn (name,body,aux uri ty left right ctx_d rest)
+ Cic.LetIn (name,body,aux uri ty left right ctx_d ctx_ty rest)
| Cic.Appl ((Cic.Const(uri_ind,ens))::tl)
when LibraryObjects.is_eq_ind_URI uri_ind ||
LibraryObjects.is_eq_ind_r_URI uri_ind ->
let is_not_fixed_lp = is_not_fixed lp in
let avoid_eq_ind = LibraryObjects.is_eq_ind_URI uri_ind in
(* extract the context and the fixed term from the predicate *)
- let m, ctx_c =
+ let m, ctx_c, ty2 =
let m, ctx_c = if is_not_fixed_lp then rp,lp else lp,rp in
(* they were under a lambda *)
- let m = CicSubstitution.subst (Cic.Implicit None) m in
+ let m = CicSubstitution.subst hole m in
let ctx_c = CicSubstitution.subst hole ctx_c in
- m, ctx_c
+ let ty2 = CicSubstitution.subst hole ty2 in
+ m, ctx_c, ty2
in
(* create the compound context and put the terms under it *)
let ctx_dc = compose_contexts ctx_d ctx_c in
(* now put the proofs in the compound context *)
let p1 = (* p1: dc_what = d_m *)
if is_not_fixed_lp then
- aux uri ty1 c_what m ctx_d p1
+ aux uri ty2 c_what m ctx_d ctx_ty p1
else
- mk_sym uri_sym ty d_m dc_what
- (aux uri ty1 m c_what ctx_d p1)
+ mk_sym uri_sym ctx_ty d_m dc_what
+ (aux uri ty2 m c_what ctx_d ctx_ty p1)
in
let p2 = (* p2: dc_other = dc_what *)
if avoid_eq_ind then
- mk_sym uri_sym ty dc_what dc_other
- (aux uri ty1 what other ctx_dc p2)
+ mk_sym uri_sym ctx_ty dc_what dc_other
+ (aux uri ty1 what other ctx_dc ctx_ty p2)
else
- aux uri ty1 other what ctx_dc p2
+ aux uri ty1 other what ctx_dc ctx_ty p2
in
(* if pred = \x.C[x]=m --> t : C[other]=m --> trans other what m
if pred = \x.m=C[x] --> t : m=C[other] --> trans m what other *)
dc_other,dc_what,d_m,p2,p1
else
d_m,dc_what,dc_other,
- (mk_sym uri_sym ty dc_what d_m p1),
- (mk_sym uri_sym ty dc_other dc_what p2)
+ (mk_sym uri_sym ctx_ty dc_what d_m p1),
+ (mk_sym uri_sym ctx_ty dc_other dc_what p2)
in
- mk_trans uri_trans ty a b c paeqb pbeqc
+ mk_trans uri_trans ctx_ty a b c paeqb pbeqc
+ | t when ctx_d = hole -> t
| t ->
- let uri_sym = LibraryObjects.sym_eq_URI ~eq:uri in
- let uri_ind = LibraryObjects.eq_ind_URI ~eq:uri in
+(* let uri_sym = LibraryObjects.sym_eq_URI ~eq:uri in *)
+(* let uri_ind = LibraryObjects.eq_ind_URI ~eq:uri in *)
+ let uri_feq =
+ UriManager.uri_of_string "cic:/matita/logic/equality/eq_f.con"
+ in
let pred =
- (* ctx_d will go under a lambda, but put_in_ctx substitutes Rel 1 *)
- let r = CicSubstitution.lift 1 (put_in_ctx ctx_d left) in
+(* let r = CicSubstitution.lift 1 (put_in_ctx ctx_d left) in *)
let l =
let ctx_d = CicSubstitution.lift 1 ctx_d in
put_in_ctx ctx_d (Cic.Rel 1)
in
- let lty = CicSubstitution.lift 1 ty in
- Cic.Lambda (Cic.Name "foo",ty,(mk_eq uri lty l r))
+(* let lty = CicSubstitution.lift 1 ctx_ty in *)
+(* Cic.Lambda (Cic.Name "foo",ty,(mk_eq uri lty l r)) *)
+ Cic.Lambda (Cic.Name "foo",ty,l)
in
- let d_left = put_in_ctx ctx_d left in
- let d_right = put_in_ctx ctx_d right in
- let refl_eq = mk_refl uri ty d_left in
- mk_sym uri_sym ty d_right d_left
- (mk_eq_ind uri_ind ty left pred refl_eq right t)
+(* let d_left = put_in_ctx ctx_d left in *)
+(* let d_right = put_in_ctx ctx_d right in *)
+(* let refl_eq = mk_refl uri ctx_ty d_left in *)
+(* mk_sym uri_sym ctx_ty d_right d_left *)
+(* (mk_eq_ind uri_ind ty left pred refl_eq right t) *)
+ (mk_feq uri_feq ty ctx_ty left pred right t)
in
- aux uri ty left right hole t
+ aux uri ty left right hole ty t
;;
let contextualize_rewrites t ty =
function
| Exact t -> Exact (Subst.apply_subst subst t)
| Step (s,(rule, id1, (pos,id2), pred)) ->
- Step (Subst.concat subst s,(rule, id1, (pos,id2), pred))
+ Step (Subst.concat subst s,(rule, id1, (pos,id2), pred))
;;
-let build_proof_step ?(sym=false) lift subst p1 p2 pos l r pred =
+let build_proof_step eq lift subst p1 p2 pos l r pred =
let p1 = Subst.apply_subst_lift lift subst p1 in
let p2 = Subst.apply_subst_lift lift subst p2 in
let l = CicSubstitution.lift lift l in
let p =
match pos with
| Utils.Left ->
- mk_eq_ind (Utils.eq_ind_URI ()) ty what pred p1 other p2
+ mk_eq_ind (LibraryObjects.eq_ind_URI ~eq) ty what pred p1 other p2
| Utils.Right ->
- mk_eq_ind (Utils.eq_ind_r_URI ()) ty what pred p1 other p2
+ mk_eq_ind (LibraryObjects.eq_ind_r_URI ~eq) ty what pred p1 other p2
in
- if sym then
- let uri,pl,pr =
- let eq,_,pl,pr = open_eq body in
- LibraryObjects.sym_eq_URI ~eq, pl, pr
- in
- let l = CicSubstitution.subst other pl in
- let r = CicSubstitution.subst other pr in
- mk_sym uri ty l r p
- else
p
;;
let parametrize_proof p l r ty =
- let parameters = CicUtil.metas_of_term p
-@ CicUtil.metas_of_term l
-@ CicUtil.metas_of_term r
-in (* ?if they are under a lambda? *)
+ let uniq l = HExtlib.list_uniq (List.sort Pervasives.compare l) in
+ let mot = CicUtil.metas_of_term_set in
+ let parameters = uniq (mot p @ mot l @ mot r) in
+ (* ?if they are under a lambda? *)
let parameters =
HExtlib.list_uniq (List.sort Pervasives.compare parameters)
in
| Step (_,(_,id1,(_,id2),_)) ->
let m = find_deps m id1 in
let m = find_deps m id2 in
- M.add i (M.find id1 m @ M.find id2 m @ [id1;id2]) m
+ (* without the uniq there is a stack overflow doing concatenation *)
+ let xxx = [id1;id2] @ M.find id1 m @ M.find id2 m in
+ let xxx = HExtlib.list_uniq (List.sort Pervasives.compare xxx) in
+ M.add i xxx m
;;
let topological_sort l =
(* build the partial order relation *)
- let m =
- List.fold_left (fun m i -> find_deps m i)
- M.empty l
+ let m = List.fold_left (fun m i -> find_deps m i) M.empty l in
+ let m = (* keep only deps inside l *)
+ List.fold_left
+ (fun m' i ->
+ M.add i (List.filter (fun x -> List.mem x l) (M.find i m)) m')
+ M.empty l
in
let m = M.map (fun x -> Some x) m in
(* utils *)
| Some ll -> Some (List.filter (fun i -> not (List.mem i l)) ll))
m
in
- let rec aux m =
+ let rec aux m res =
let keys = keys m in
let ok = split keys m in
let m = purge ok m in
- ok @ (if ok = [] then [] else aux m)
+ let res = ok @ res in
+ if ok = [] then res else aux m res
in
- aux m
+ let rc = List.rev (aux m []) in
+ rc
;;
(* now h is complete *)
let proofs = Hashtbl.fold (fun k count acc-> (k,count)::acc) h [] in
let proofs = List.filter (fun (_,c) -> c > 1) proofs in
- topological_sort (List.map (fun (i,_) -> i) proofs)
+ let res = topological_sort (List.map (fun (i,_) -> i) proofs) in
+ res
;;
-let build_proof_term h lift proof =
+let build_proof_term eq h lift proof =
let proof_of_id aux id =
let p,l,r = proof_of_id id in
try List.assoc id h,l,r with Not_found -> aux p, l, r
in
let rec aux = function
- | Exact term -> CicSubstitution.lift lift term
+ | Exact term ->
+ CicSubstitution.lift lift term
| Step (subst,(rule, id1, (pos,id2), pred)) ->
let p1,_,_ = proof_of_id aux id1 in
let p2,l,r = proof_of_id aux id2 in
| Cic.Lambda (_,a,b) -> Cic.Lambda (varname,a,b)
| _ -> assert false
in
- let p = build_proof_step lift subst p1 p2 pos l r pred in
+ let p = build_proof_step eq lift subst p1 p2 pos l r pred in
(* let cond = (not (List.mem 302 (Utils.metas_of_term p)) || id1 = 8 || id1 = 132) in
if not cond then
prerr_endline ("ERROR " ^ string_of_int id1 ^ " " ^ string_of_int id2);
aux proof
;;
-let build_goal_proof l initial ty se =
+let build_goal_proof eq l initial ty se context menv =
let se = List.map (fun i -> Cic.Meta (i,[])) se in
let lets = get_duplicate_step_in_wfo l initial in
let letsno = List.length lets in
let _,mty,_,_ = open_eq ty in
- let lift_list l = List.map (fun (i,t) -> i,CicSubstitution.lift 1 t) l
- in
+ let lift_list l = List.map (fun (i,t) -> i,CicSubstitution.lift 1 t) l in
let lets,_,h =
List.fold_left
(fun (acc,n,h) id ->
let p,l,r = proof_of_id id in
- let cic = build_proof_term h n p in
+ let cic = build_proof_term eq h n p in
let real_cic,instance =
parametrize_proof cic l r (CicSubstitution.lift n mty)
in
| [] -> current_proof,se
| (rule,pos,id,subst,pred)::tl ->
let p,l,r = proof_of_id id in
- let p = build_proof_term h letsno p in
+ let p = build_proof_term eq h letsno p in
let pos = if pos = Utils.Left then Utils.Right else Utils.Left in
let varname =
match rule with
| _ -> assert false
in
let proof =
- build_proof_step letsno subst current_proof p pos l r pred
+ build_proof_step eq letsno subst current_proof p pos l r pred
in
let proof,se = aux se proof tl in
Subst.apply_subst_lift letsno subst proof,
List.map (fun x -> Subst.apply_subst_lift letsno subst x) se
in
- aux se (build_proof_term h letsno initial) l
+ aux se (build_proof_term eq h letsno initial) l
in
let n,proof =
let initial = proof in
cic, p))
lets (letsno-1,initial)
in
- (proof,se)
- (* canonical (contextualize_rewrites proof (CicSubstitution.lift letsno ty)),
- se *)
+ canonical
+ (contextualize_rewrites proof (CicSubstitution.lift letsno ty))
+ context menv,
+ se
;;
-let refl_proof ty term =
- Cic.Appl
- [Cic.MutConstruct
- (LibraryObjects.eq_URI (), 0, 1, []);
- ty; term]
+let refl_proof eq_uri ty term =
+ Cic.Appl [Cic.MutConstruct (eq_uri, 0, 1, []); ty; term]
;;
let metas_of_proof p =
- let p = build_proof_term [] 0 p in
+ let eq =
+ match LibraryObjects.eq_URI () with
+ | Some u -> u
+ | None ->
+ raise
+ (ProofEngineTypes.Fail
+ (lazy "No default equality defined when calling metas_of_proof"))
+ in
+ let p = build_proof_term eq [] 0 p in
Utils.metas_of_term p
;;
+let remove_local_context eq =
+ let w, p, (ty, left, right, o), menv,id = open_equality eq in
+ let p = Utils.remove_local_context p in
+ let ty = Utils.remove_local_context ty in
+ let left = Utils.remove_local_context left in
+ let right = Utils.remove_local_context right in
+ w, p, (ty, left, right, o), menv, id
+;;
+
let relocate newmeta menv to_be_relocated =
let subst, newmetasenv, newmeta =
List.fold_right
let menv = Subst.apply_subst_metasenv subst menv @ newmetasenv in
subst, menv, newmeta
+let fix_metas_goal newmeta goal =
+ let (proof, menv, ty) = goal in
+ let to_be_relocated =
+ HExtlib.list_uniq (List.sort Pervasives.compare (Utils.metas_of_term ty))
+ in
+ let subst, menv, newmeta = relocate newmeta menv to_be_relocated in
+ let ty = Subst.apply_subst subst ty in
+ let proof =
+ match proof with
+ | [] -> assert false (* is a nonsense to relocate the initial goal *)
+ | (r,pos,id,s,p) :: tl -> (r,pos,id,Subst.concat subst s,p) :: tl
+ in
+ newmeta+1,(proof, menv, ty)
+;;
let fix_metas newmeta eq =
let w, p, (ty, left, right, o), menv,_ = open_equality eq in
let rec aux ((table_l, table_r) as table) t1 t2 =
match t1, t2 with
| C.Meta (m1, tl1), C.Meta (m2, tl2) ->
+ let tl1, tl2 = [],[] in
let m1_binding, table_l =
try List.assoc m1 table_l, table_l
with Not_found -> m2, (m1, m2)::table_l
exception TermIsNotAnEquality;;
let term_is_equality term =
- let iseq uri = UriManager.eq uri (LibraryObjects.eq_URI ()) in
match term with
- | Cic.Appl [Cic.MutInd (uri, _, _); _; _; _] when iseq uri -> true
+ | Cic.Appl [Cic.MutInd (uri, _, _); _; _; _]
+ when LibraryObjects.is_eq_URI uri -> true
| _ -> false
;;
let equality_of_term proof term =
- let eq_uri = LibraryObjects.eq_URI () in
- let iseq uri = UriManager.eq uri eq_uri in
match term with
- | Cic.Appl [Cic.MutInd (uri, _, _); ty; t1; t2] when iseq uri ->
+ | Cic.Appl [Cic.MutInd (uri, _, _); ty; t1; t2]
+ when LibraryObjects.is_eq_URI uri ->
let o = !Utils.compare_terms t1 t2 in
let stat = (ty,t1,t2,o) in
let w = Utils.compute_equality_weight stat in
;;
-let term_of_equality equality =
+let term_of_equality eq_uri equality =
let _, _, (ty, left, right, _), menv, _= open_equality equality in
let eq i = function Cic.Meta (j, _) -> i = j | _ -> false in
let argsno = List.length menv in
let t =
CicSubstitution.lift argsno
- (Cic.Appl [Cic.MutInd (LibraryObjects.eq_URI (), 0, []); ty; left; right])
+ (Cic.Appl [Cic.MutInd (eq_uri, 0, []); ty; left; right])
in
snd (
List.fold_right
(Demodulation,id1,(Utils.Left,id),pred))
;;
+module IntOT = struct
+ type t = int
+ let compare = Pervasives.compare
+end
+
+module IntSet = Set.Make(IntOT);;
+
+let n_purged = ref 0;;
+
+let collect alive1 alive2 alive3 =
+ let _ = <:start<collect>> in
+ let deps_of id =
+ let p,_,_ = proof_of_id id in
+ match p with
+ | Exact _ -> IntSet.empty
+ | Step (_,(_,id1,(_,id2),_)) ->
+ IntSet.add id1 (IntSet.add id2 IntSet.empty)
+ in
+ let rec close s =
+ let news = IntSet.fold (fun id s -> IntSet.union (deps_of id) s) s s in
+ if IntSet.equal news s then s else close news
+ in
+ let l_to_s s l = List.fold_left (fun s x -> IntSet.add x s) s l in
+ let alive_set = l_to_s (l_to_s (l_to_s IntSet.empty alive2) alive1) alive3 in
+ let closed_alive_set = close alive_set in
+ let to_purge =
+ Hashtbl.fold
+ (fun k _ s ->
+ if not (IntSet.mem k closed_alive_set) then
+ k::s else s) id_to_eq []
+ in
+ n_purged := !n_purged + List.length to_purge;
+ List.iter (Hashtbl.remove id_to_eq) to_purge;
+ let _ = <:stop<collect>> in ()
+;;
+
+let id_of e =
+ let _,_,_,_,id = open_equality e in id
+;;
+
+let get_stats () =
+ <:show<Equality.>> ^
+ "# of purged eq by the collector: " ^ string_of_int !n_purged ^ "\n"
+;;