X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Focaml%2Fcic_unification%2FcicUnification.ml;h=35eb18f450974d61fc238b77d3f985203b249d6b;hb=c5d5bf37b1e4c4b9b499ed2cbfe27cf2ec181944;hp=a01f9a9b8596bf76dda9745a3c4ebd0142551d47;hpb=faf01084c13ccd731d7040fadb96caa0a2aa0019;p=helm.git diff --git a/helm/ocaml/cic_unification/cicUnification.ml b/helm/ocaml/cic_unification/cicUnification.ml index a01f9a9b8..35eb18f45 100644 --- a/helm/ocaml/cic_unification/cicUnification.ml +++ b/helm/ocaml/cic_unification/cicUnification.ml @@ -23,338 +23,289 @@ * http://cs.unibo.it/helm/. *) -exception UnificationFailed;; -exception Free;; -exception OccurCheck;; +open Printf -type substitution = (int * Cic.term) list +exception UnificationFailure of string;; +exception Uncertain of string;; +exception AssertFailure of string;; -(*CSC: Hhhmmm. Forse dovremmo spostarla in CicSubstitution dove si trova la *) -(*CSC: lift? O creare una proofEngineSubstitution? *) -(* the function delift n m un-lifts a lambda term m of n level of abstractions. - It returns an exception Free if M contains a free variable in the range 1--n *) -let delift n = - let rec deliftaux k = - let module C = Cic in - function - C.Rel m -> - if m < k then C.Rel m else - if m < k+n then raise Free - else C.Rel (m - n) - | C.Var _ as t -> t - | C.Meta _ as t -> t - | C.Sort _ as t -> t - | C.Implicit as t -> t - | C.Cast (te,ty) -> C.Cast (deliftaux k te, deliftaux k ty) - | C.Prod (n,s,t) -> C.Prod (n, deliftaux k s, deliftaux (k+1) t) - | C.Lambda (n,s,t) -> C.Lambda (n, deliftaux k s, deliftaux (k+1) t) - | C.LetIn (n,s,t) -> C.LetIn (n, deliftaux k s, deliftaux (k+1) t) - | C.Appl l -> C.Appl (List.map (deliftaux k) l) - | C.Const _ as t -> t - | C.Abst _ as t -> t - | C.MutInd _ as t -> t - | C.MutConstruct _ as t -> t - | C.MutCase (sp,cookingsno,i,outty,t,pl) -> - C.MutCase (sp, cookingsno, i, deliftaux k outty, deliftaux k t, - List.map (deliftaux k) pl) - | C.Fix (i, fl) -> - let len = List.length fl in - let liftedfl = - List.map - (fun (name, i, ty, bo) -> (name, i, deliftaux k ty, deliftaux (k+len) bo)) - fl - in - C.Fix (i, liftedfl) - | C.CoFix (i, fl) -> - let len = List.length fl in - let liftedfl = - List.map - (fun (name, ty, bo) -> (name, deliftaux k ty, deliftaux (k+len) bo)) - fl - in - C.CoFix (i, liftedfl) - in - if n = 0 then - (function t -> t) - else - deliftaux 1 -;; +let debug_print = prerr_endline + +let type_of_aux' metasenv subst context term = + try + CicMetaSubst.type_of_aux' metasenv subst context term + with + | CicMetaSubst.MetaSubstFailure msg -> + raise (AssertFailure + ((sprintf + "Type checking error: %s in context\n%s\nand metasenv\n%s.\nException: %s.\nBroken invariant: unification must be invoked only on well typed terms" + (CicMetaSubst.ppterm subst term) + (CicMetaSubst.ppcontext subst context) + (CicMetaSubst.ppmetasenv metasenv subst) msg))) (* NUOVA UNIFICAZIONE *) (* A substitution is a (int * Cic.term) list that associates a metavariable i with its body. A metaenv is a (int * Cic.term) list that associate a metavariable i with is type. - fo_unif_new takes a metasenv, a context, - two terms t1 and t2 and gives back a new - substitution which is _NOT_ unwinded. It must be unwinded before + fo_unif_new takes a metasenv, a context, two terms t1 and t2 and gives back + a new substitution which is _NOT_ unwinded. It must be unwinded before applying it. *) - -let fo_unif_new metasenv context t1 t2 = - let module C = Cic in - let module R = CicReduction in - let module S = CicSubstitution in - let rec fo_unif_aux subst k t1 t2 = - match (t1, t2) with - (C.Meta n, C.Meta m) -> if n == m then subst - else let subst'= - let tn = try List.assoc n subst - with Not_found -> C.Meta n in - let tm = try List.assoc m subst - with Not_found -> C.Meta m in - (match (tn, tm) with - (C.Meta n, C.Meta m) -> if n==m then subst - else if n (n, tm)::subst - | (tn, C.Meta m) -> (m, tn)::subst - | (tn,tm) -> fo_unif_aux subst 0 tn tm) in - (* unify types first *) - let tyn = List.assoc n metasenv in - let tym = List.assoc m metasenv in - fo_unif_aux subst' 0 tyn tym - | (C.Meta n, t) - | (t, C.Meta n) -> (* unify types first *) - let t' = delift k t in - let subst' = - (try fo_unif_aux subst 0 (List.assoc n subst) t' - with Not_found -> (n, t')::subst) in - let tyn = List.assoc n metasenv in - let tyt = CicTypeChecker.type_of_aux' metasenv context t' in - fo_unif_aux subst' 0 tyn tyt - | (C.Rel _, _) - | (_, C.Rel _) - | (C.Var _, _) - | (_, C.Var _) - | (C.Sort _ ,_) - | (_, C.Sort _) - | (C.Implicit, _) - | (_, C.Implicit) -> if R.are_convertible t1 t2 then subst - else raise UnificationFailed - | (C.Cast (te,ty), t2) -> fo_unif_aux subst k te t2 - | (t1, C.Cast (te,ty)) -> fo_unif_aux subst k t1 te - | (C.Prod (_,s1,t1), C.Prod (_,s2,t2)) -> - let subst' = fo_unif_aux subst k s1 s2 in - fo_unif_aux subst' (k+1) t1 t2 - | (C.Lambda (_,s1,t1), C.Lambda (_,s2,t2)) -> - let subst' = fo_unif_aux subst k s1 s2 in - fo_unif_aux subst' (k+1) t1 t2 - | (C.LetIn (_,s1,t1), t2) -> fo_unif_aux subst k (S.subst s1 t1) t2 - | (t1, C.LetIn (_,s2,t2)) -> fo_unif_aux subst k t1 (S.subst s2 t2) - | (C.Appl l1, C.Appl l2) -> - let lr1 = List.rev l1 in - let lr2 = List.rev l2 in - let rec fo_unif_l subst = function - [],_ - | _,[] -> assert false - | ([h1],[h2]) -> fo_unif_aux subst k h1 h2 - | ([h],l) - | (l,[h]) -> fo_unif_aux subst k h (C.Appl l) - | ((h1::l1),(h2::l2)) -> - let subst' = fo_unif_aux subst k h1 h2 in - fo_unif_l subst' (l1,l2) - in - fo_unif_l subst (lr1, lr2) - | (C.Const _, _) - | (_, C.Const _) - | (C.Abst _, _) - | (_, C.Abst _) - | (C.MutInd _, _) - | (_, C.MutInd _) - | (C.MutConstruct _, _) - | (_, C.MutConstruct _) -> if R.are_convertible t1 t2 then subst - else raise UnificationFailed - | (C.MutCase (_,_,_,outt1,t1,pl1), C.MutCase (_,_,_,outt2,t2,pl2))-> - let subst' = fo_unif_aux subst k outt1 outt2 in - let subst'' = fo_unif_aux subst' k t1 t2 in - List.fold_left2 (function subst -> fo_unif_aux subst k) subst'' pl1 pl2 - | (C.Fix _, _) - | (_, C.Fix _) - | (C.CoFix _, _) - | (_, C.CoFix _) -> if R.are_convertible t1 t2 then subst - else raise UnificationFailed - | (_,_) -> raise UnificationFailed - in fo_unif_aux [] 0 t1 t2;; - -(* unwind mgu mark m applies mgu to the term m; mark is an array of integers -mark.(n) = 0 if the term has not been unwinded, is 2 if it is under uwinding, -and is 1 if it has been succesfully unwinded. Meeting the value 2 during -the computation is an error: occur-check *) -let unwind subst unwinded t = - let unwinded = ref unwinded in - let frozen = ref [] in - let rec um_aux k = - let module C = Cic in - let module S = CicSubstitution in - function - C.Rel _ as t -> t - | C.Var _ as t -> t - | C.Meta i as t ->(try S.lift k (List.assoc i !unwinded) - with Not_found -> - if List.mem i !frozen then - raise OccurCheck - else - let saved_frozen = !frozen in - frozen := i::!frozen ; - let res = - try - let t = List.assoc i subst in - let t' = um_aux 0 t in - unwinded := (i,t)::!unwinded ; - S.lift k t' - with - Not_found -> - (* not constrained variable, i.e. free in subst *) - C.Meta i - in - frozen := saved_frozen ; - res - ) - | C.Sort _ as t -> t - | C.Implicit as t -> t - | C.Cast (te,ty) -> C.Cast (um_aux k te, um_aux k ty) - | C.Prod (n,s,t) -> C.Prod (n, um_aux k s, um_aux (k+1) t) - | C.Lambda (n,s,t) -> C.Lambda (n, um_aux k s, um_aux (k+1) t) - | C.LetIn (n,s,t) -> C.LetIn (n, um_aux k s, um_aux (k+1) t) - | C.Appl (he::tl) -> - let tl' = List.map (um_aux k) tl in - begin - match um_aux k he with - C.Appl l -> C.Appl (l@tl') - | _ as he' -> C.Appl (he'::tl') - end - | C.Appl _ -> assert false - | C.Const _ as t -> t - | C.Abst _ as t -> t - | C.MutInd _ as t -> t - | C.MutConstruct _ as t -> t - | C.MutCase (sp,cookingsno,i,outty,t,pl) -> - C.MutCase (sp, cookingsno, i, um_aux k outty, um_aux k t, - List.map (um_aux k) pl) - | C.Fix (i, fl) -> - let len = List.length fl in - let liftedfl = - List.map - (fun (name, i, ty, bo) -> (name, i, um_aux k ty, um_aux (k+len) bo)) - fl +let rec fo_unif_subst test_equality_only subst context metasenv t1 t2 = + let module C = Cic in + let module R = CicMetaSubst in + let module S = CicSubstitution in + match (t1, t2) with + (C.Meta (n,ln), C.Meta (m,lm)) when n=m -> + let ok,subst,metasenv = + try + List.fold_left2 + (fun (b,subst,metasenv) t1 t2 -> + if b then true,subst,metasenv else + match t1,t2 with + None,_ + | _,None -> true,subst,metasenv + | Some t1', Some t2' -> + (* First possibility: restriction *) + (* Second possibility: unification *) + (* Third possibility: convertibility *) + if R.are_convertible subst context t1' t2' then + true,subst,metasenv + else + (try + let subst,metasenv = + fo_unif_subst + test_equality_only subst context metasenv t1' t2' + in + true,subst,metasenv + with + Not_found -> false,subst,metasenv) + ) (true,subst,metasenv) ln lm + with + Invalid_argument _ -> + raise (UnificationFailure (sprintf + "Error trying to unify %s with %s: the lengths of the two local contexts do not match." (CicMetaSubst.ppterm subst t1) (CicMetaSubst.ppterm subst t2))) in - C.Fix (i, liftedfl) - | C.CoFix (i, fl) -> - let len = List.length fl in - let liftedfl = - List.map - (fun (name, ty, bo) -> (name, um_aux k ty, um_aux (k+len) bo)) - fl + if ok then + subst,metasenv + else + raise (UnificationFailure (sprintf + "Error trying to unify %s with %s: the algorithm tried to check whether the two substitutions are convertible; if they are not, it tried to unify the two substitutions. No restriction was attempted." + (CicMetaSubst.ppterm subst t1) (CicMetaSubst.ppterm subst t2))) + | (C.Meta (n,_), C.Meta (m,_)) when n>m -> + fo_unif_subst test_equality_only subst context metasenv t2 t1 + | (C.Meta (n,l), t) + | (t, C.Meta (n,l)) -> + let swap = + match t1,t2 with + C.Meta (n,_), C.Meta (m,_) when n < m -> false + | _, C.Meta _ -> false + | _,_ -> true in - C.CoFix (i, liftedfl) - in - um_aux 0 t,!unwinded -;; - -(* apply_subst_reducing subst (Some (mtr,reductions_no)) t *) -(* performs as (apply_subst subst t) until it finds an application of *) -(* (META [meta_to_reduce]) that, once unwinding is performed, creates *) -(* a new beta-redex; in this case up to [reductions_no] consecutive *) -(* beta-reductions are performed. *) -(* Hint: this function is usually called when [reductions_no] *) -(* eta-expansions have been performed and the head of the new *) -(* application has been unified with (META [meta_to_reduce]): *) -(* during the unwinding the eta-expansions are undone. *) - -let apply_subst_reducing subst meta_to_reduce t = - let unwinded = ref subst in - let rec um_aux k = - let module C = Cic in - let module S = CicSubstitution in - function - C.Rel _ as t -> t - | C.Var _ as t -> t - | C.Meta i as t -> - (try - S.lift k (List.assoc i !unwinded) + let lower = fun x y -> if swap then y else x in + let upper = fun x y -> if swap then x else y in + let fo_unif_subst_ordered + test_equality_only subst context metasenv m1 m2 = + fo_unif_subst test_equality_only subst context metasenv + (lower m1 m2) (upper m1 m2) + in + let subst'',metasenv' = + try + let oldt = (List.assoc n subst) in + let lifted_oldt = S.lift_meta l oldt in + fo_unif_subst_ordered + test_equality_only subst context metasenv t lifted_oldt with Not_found -> - C.Meta i) - | C.Sort _ as t -> t - | C.Implicit as t -> t - | C.Cast (te,ty) -> C.Cast (um_aux k te, um_aux k ty) - | C.Prod (n,s,t) -> C.Prod (n, um_aux k s, um_aux (k+1) t) - | C.Lambda (n,s,t) -> C.Lambda (n, um_aux k s, um_aux (k+1) t) - | C.LetIn (n,s,t) -> C.LetIn (n, um_aux k s, um_aux (k+1) t) - | C.Appl (he::tl) -> - let tl' = List.map (um_aux k) tl in - let t' = - match um_aux k he with - C.Appl l -> C.Appl (l@tl') - | _ as he' -> C.Appl (he'::tl') - in - begin - match meta_to_reduce with - Some (mtr,reductions_no) when he = C.Meta mtr -> - let rec beta_reduce = - function - (n,(C.Appl (C.Lambda (_,_,t)::he'::tl'))) when n > 0 -> - let he'' = CicSubstitution.subst he' t in - if tl' = [] then - he'' - else - beta_reduce (n-1,C.Appl(he''::tl')) - | (_,t) -> t - in - beta_reduce (reductions_no,t') - | _ -> t' - end - | C.Appl _ -> assert false - | C.Const _ as t -> t - | C.Abst _ as t -> t - | C.MutInd _ as t -> t - | C.MutConstruct _ as t -> t - | C.MutCase (sp,cookingsno,i,outty,t,pl) -> - C.MutCase (sp, cookingsno, i, um_aux k outty, um_aux k t, - List.map (um_aux k) pl) - | C.Fix (i, fl) -> - let len = List.length fl in - let liftedfl = - List.map - (fun (name, i, ty, bo) -> (name, i, um_aux k ty, um_aux (k+len) bo)) - fl + let t',metasenv',subst' = + try + CicMetaSubst.delift n subst context metasenv l t + with + (CicMetaSubst.MetaSubstFailure msg)-> raise(UnificationFailure msg) + | (CicMetaSubst.Uncertain msg) -> raise (Uncertain msg) + in + let t'' = + match t' with + C.Sort (C.Type u) when not test_equality_only -> + let u' = CicUniv.fresh () in + let s = C.Sort (C.Type u') in + ignore (CicUniv.add_ge (upper u u') (lower u u')) ; + s + | _ -> t' + in + (n, t'')::subst', metasenv' in - C.Fix (i, liftedfl) - | C.CoFix (i, fl) -> - let len = List.length fl in - let liftedfl = - List.map - (fun (name, ty, bo) -> (name, um_aux k ty, um_aux (k+len) bo)) - fl + let (_,_,meta_type) = CicUtil.lookup_meta n metasenv' in + (try + let tyt = + type_of_aux' metasenv' subst'' context t + in + fo_unif_subst + test_equality_only + subst'' context metasenv' tyt (S.lift_meta l meta_type) + with AssertFailure _ -> + (* TODO huge hack!!!! + * we keep on unifying/refining in the hope that the problem will be + * eventually solved. In the meantime we're breaking a big invariant: + * the terms that we are unifying are no longer well typed in the + * current context (in the worst case we could even diverge) + *) +(* +prerr_endline "********* FROM NOW ON EVERY REASONABLE INVARIANT IS BROKEN."; +prerr_endline "********* PROCEED AT YOUR OWN RISK. AND GOOD LUCK." ; +*) + (subst'', metasenv')) + | (C.Var (uri1,exp_named_subst1),C.Var (uri2,exp_named_subst2)) + | (C.Const (uri1,exp_named_subst1),C.Const (uri2,exp_named_subst2)) -> + if UriManager.eq uri1 uri2 then + fo_unif_subst_exp_named_subst test_equality_only subst context metasenv + exp_named_subst1 exp_named_subst2 + else + raise (UnificationFailure (sprintf + "Can't unify %s with %s due to different constants" + (CicMetaSubst.ppterm subst t1) (CicMetaSubst.ppterm subst t2))) + | C.MutInd (uri1,i1,exp_named_subst1),C.MutInd (uri2,i2,exp_named_subst2) -> + if UriManager.eq uri1 uri2 && i1 = i2 then + fo_unif_subst_exp_named_subst test_equality_only subst context metasenv + exp_named_subst1 exp_named_subst2 + else + raise (UnificationFailure (sprintf + "Can't unify %s with %s due to different inductive principles" + (CicMetaSubst.ppterm subst t1) (CicMetaSubst.ppterm subst t2))) + | C.MutConstruct (uri1,i1,j1,exp_named_subst1), + C.MutConstruct (uri2,i2,j2,exp_named_subst2) -> + if UriManager.eq uri1 uri2 && i1 = i2 && j1 = j2 then + fo_unif_subst_exp_named_subst test_equality_only subst context metasenv + exp_named_subst1 exp_named_subst2 + else + raise (UnificationFailure (sprintf + "Can't unify %s with %s due to different inductive constructors" + (CicMetaSubst.ppterm subst t1) (CicMetaSubst.ppterm subst t2))) + | (C.Implicit _, _) | (_, C.Implicit _) -> assert false + | (C.Cast (te,ty), t2) -> fo_unif_subst test_equality_only + subst context metasenv te t2 + | (t1, C.Cast (te,ty)) -> fo_unif_subst test_equality_only + subst context metasenv t1 te + | (C.Prod (n1,s1,t1), C.Prod (_,s2,t2)) -> + (* TASSI: this is the only case in which we want == *) + let subst',metasenv' = fo_unif_subst true + subst context metasenv s1 s2 in + fo_unif_subst test_equality_only + subst' ((Some (n1,(C.Decl s1)))::context) metasenv' t1 t2 + | (C.Lambda (n1,s1,t1), C.Lambda (_,s2,t2)) -> + (* TASSI: ask someone a reason for not putting true here *) + let subst',metasenv' = fo_unif_subst test_equality_only + subst context metasenv s1 s2 in + fo_unif_subst test_equality_only + subst' ((Some (n1,(C.Decl s1)))::context) metasenv' t1 t2 + | (C.LetIn (_,s1,t1), t2) + | (t2, C.LetIn (_,s1,t1)) -> + fo_unif_subst + test_equality_only subst context metasenv t2 (S.subst s1 t1) + | (C.Appl l1, C.Appl l2) -> + let lr1 = List.rev l1 in + let lr2 = List.rev l2 in + let rec fo_unif_l test_equality_only subst metasenv = + function + [],_ + | _,[] -> assert false + | ([h1],[h2]) -> + fo_unif_subst test_equality_only subst context metasenv h1 h2 + | ([h],l) + | (l,[h]) -> + fo_unif_subst + test_equality_only subst context metasenv h (C.Appl (List.rev l)) + | ((h1::l1),(h2::l2)) -> + let subst', metasenv' = + fo_unif_subst test_equality_only subst context metasenv h1 h2 + in + fo_unif_l test_equality_only subst' metasenv' (l1,l2) in - C.CoFix (i, liftedfl) - in - um_aux 0 t -;; + fo_unif_l test_equality_only subst metasenv (lr1, lr2) + | (C.MutCase (_,_,outt1,t1',pl1), C.MutCase (_,_,outt2,t2',pl2))-> + let subst', metasenv' = + fo_unif_subst test_equality_only subst context metasenv outt1 outt2 in + let subst'',metasenv'' = + fo_unif_subst test_equality_only subst' context metasenv' t1' t2' in + (try + List.fold_left2 + (function (subst,metasenv) -> + fo_unif_subst test_equality_only subst context metasenv + ) (subst'',metasenv'') pl1 pl2 + with + Invalid_argument _ -> + raise (UnificationFailure (sprintf + "Error trying to unify %s with %s: the number of branches is not the same." (CicMetaSubst.ppterm subst t1) (CicMetaSubst.ppterm subst t2)))) + | (C.Rel _, _) | (_, C.Rel _) + | (C.Sort _ ,_) | (_, C.Sort _) + | (C.Const _, _) | (_, C.Const _) + | (C.MutInd _, _) | (_, C.MutInd _) + | (C.MutConstruct _, _) | (_, C.MutConstruct _) + | (C.Fix _, _) | (_, C.Fix _) + | (C.CoFix _, _) | (_, C.CoFix _) -> + if R.are_convertible subst context t1 t2 then + subst, metasenv + else + raise (UnificationFailure (sprintf + "Can't unify %s with %s because they are not convertible" + (CicMetaSubst.ppterm subst t1) (CicMetaSubst.ppterm subst t2))) + | (_,_) -> + if R.are_convertible subst context t1 t2 then + subst, metasenv + else + raise (UnificationFailure (sprintf + "Can't unify %s with %s because they are not convertible" + (CicMetaSubst.ppterm subst t1) (CicMetaSubst.ppterm subst t2))) -(* UNWIND THE MGU INSIDE THE MGU *) -(* let unwind mgu = - let mark = Array.make (Array.length mgu) 0 in - Array.iter (fun x -> let foo = unwind_meta mgu mark x in ()) mgu; mgu;; *) +and fo_unif_subst_exp_named_subst test_equality_only subst context metasenv + exp_named_subst1 exp_named_subst2 += + try + List.fold_left2 + (fun (subst,metasenv) (uri1,t1) (uri2,t2) -> + assert (uri1=uri2) ; + fo_unif_subst test_equality_only subst context metasenv t1 t2 + ) (subst,metasenv) exp_named_subst1 exp_named_subst2 + with + Invalid_argument _ -> + let print_ens ens = + String.concat " ; " + (List.map + (fun (uri,t) -> + UriManager.string_of_uri uri ^ " := " ^ (CicMetaSubst.ppterm subst t) + ) ens) + in + raise (UnificationFailure (sprintf + "Error trying to unify the two explicit named substitutions (local contexts) %s and %s: their lengths is different." (print_ens exp_named_subst1) (print_ens exp_named_subst2))) -let unwind_subst subst = - List.fold_left - (fun unwinded (i,_) -> snd (unwind subst unwinded (Cic.Meta i))) [] subst -;; +(* A substitution is a (int * Cic.term) list that associates a *) +(* metavariable i with its body. *) +(* metasenv is of type Cic.metasenv *) +(* fo_unif takes a metasenv, a context, two terms t1 and t2 and gives back *) +(* a new substitution which is already unwinded and ready to be applied and *) +(* a new metasenv in which some hypothesis in the contexts of the *) +(* metavariables may have been restricted. *) +let fo_unif metasenv context t1 t2 = + fo_unif_subst false [] context metasenv t1 t2 ;; -let apply_subst subst t = - fst (unwind [] subst t) +let fo_unif_subst subst context metasenv t1 t2 = + let enrich_msg msg = + sprintf "Unification error unifying %s of type %s with %s of type %s in context\n%s\nand metasenv\n%s\nbecause %s" + (CicMetaSubst.ppterm subst t1) + (try + CicPp.ppterm (type_of_aux' metasenv subst context t1) + with _ -> "MALFORMED") + (CicMetaSubst.ppterm subst t2) + (try + CicPp.ppterm (type_of_aux' metasenv subst context t2) + with _ -> "MALFORMED") + (CicMetaSubst.ppcontext subst context) + (CicMetaSubst.ppmetasenv metasenv subst) msg + in + try + fo_unif_subst false subst context metasenv t1 t2 + with + | AssertFailure msg -> raise (AssertFailure (enrich_msg msg)) + | UnificationFailure msg -> raise (UnificationFailure (enrich_msg msg)) ;; -(* A substitution is a (int * Cic.term) list that associates a - metavariable i with its body. - A metaenv is a (int * Cic.term) list that associate a metavariable - i with is type. - fo_unif takes a metasenv, a context, - two terms t1 and t2 and gives back a new - substitution which is already unwinded and ready to be applied. *) -let fo_unif metasenv context t1 t2 = - let subst_to_unwind = fo_unif_new metasenv context t1 t2 in - unwind_subst subst_to_unwind -;;