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|
(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2012 *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(************************************************************************)
open Util
open Term
open Termops
open Reductionops
exception UFAIL of constr*constr
(*
RIGID-only Martelli-Montanari style unification for CLOSED terms
I repeat : t1 and t2 must NOT have ANY free deBruijn
sigma is kept normal with respect to itself but is lazily applied
to the equation set. Raises UFAIL with a pair of terms
*)
let unif t1 t2=
let bige=Queue.create ()
and sigma=ref [] in
let bind i t=
sigma:=(i,t)::
(List.map (function (n,tn)->(n,subst_meta [i,t] tn)) !sigma) in
let rec head_reduce t=
(* forbids non-sigma-normal meta in head position*)
match kind_of_term t with
Meta i->
(try
head_reduce (List.assoc i !sigma)
with Not_found->t)
| _->t in
Queue.add (t1,t2) bige;
try while true do
let t1,t2=Queue.take bige in
let nt1=head_reduce (whd_betaiotazeta Evd.empty t1)
and nt2=head_reduce (whd_betaiotazeta Evd.empty t2) in
match (kind_of_term nt1),(kind_of_term nt2) with
Meta i,Meta j->
if i<>j then
if i<j then bind j nt1
else bind i nt2
| Meta i,_ ->
let t=subst_meta !sigma nt2 in
if Intset.is_empty (free_rels t) &&
not (occur_term (mkMeta i) t) then
bind i t else raise (UFAIL(nt1,nt2))
| _,Meta i ->
let t=subst_meta !sigma nt1 in
if Intset.is_empty (free_rels t) &&
not (occur_term (mkMeta i) t) then
bind i t else raise (UFAIL(nt1,nt2))
| Cast(_,_,_),_->Queue.add (strip_outer_cast nt1,nt2) bige
| _,Cast(_,_,_)->Queue.add (nt1,strip_outer_cast nt2) bige
| (Prod(_,a,b),Prod(_,c,d))|(Lambda(_,a,b),Lambda(_,c,d))->
Queue.add (a,c) bige;Queue.add (pop b,pop d) bige
| Case (_,pa,ca,va),Case (_,pb,cb,vb)->
Queue.add (pa,pb) bige;
Queue.add (ca,cb) bige;
let l=Array.length va in
if l<>(Array.length vb) then
raise (UFAIL (nt1,nt2))
else
for i=0 to l-1 do
Queue.add (va.(i),vb.(i)) bige
done
| App(ha,va),App(hb,vb)->
Queue.add (ha,hb) bige;
let l=Array.length va in
if l<>(Array.length vb) then
raise (UFAIL (nt1,nt2))
else
for i=0 to l-1 do
Queue.add (va.(i),vb.(i)) bige
done
| _->if not (eq_constr nt1 nt2) then raise (UFAIL (nt1,nt2))
done;
assert false
(* this place is unreachable but needed for the sake of typing *)
with Queue.Empty-> !sigma
let value i t=
let add x y=
if x<0 then y else if y<0 then x else x+y in
let rec vaux term=
if isMeta term && destMeta term = i then 0 else
let f v t=add v (vaux t) in
let vr=fold_constr f (-1) term in
if vr<0 then -1 else vr+1 in
vaux t
type instance=
Real of (int*constr)*int
| Phantom of constr
let mk_rel_inst t=
let new_rel=ref 1 in
let rel_env=ref [] in
let rec renum_rec d t=
match kind_of_term t with
Meta n->
(try
mkRel (d+(List.assoc n !rel_env))
with Not_found->
let m= !new_rel in
incr new_rel;
rel_env:=(n,m) :: !rel_env;
mkRel (m+d))
| _ -> map_constr_with_binders succ renum_rec d t
in
let nt=renum_rec 0 t in (!new_rel - 1,nt)
let unif_atoms i dom t1 t2=
try
let t=List.assoc i (unif t1 t2) in
if isMeta t then Some (Phantom dom)
else Some (Real(mk_rel_inst t,value i t1))
with
UFAIL(_,_) ->None
| Not_found ->Some (Phantom dom)
let renum_metas_from k n t= (* requires n = max (free_rels t) *)
let l=List.tabulate (fun i->mkMeta (k+i)) n in
substl l t
let more_general (m1,t1) (m2,t2)=
let mt1=renum_metas_from 0 m1 t1
and mt2=renum_metas_from m1 m2 t2 in
try
let sigma=unif mt1 mt2 in
let p (n,t)= n<m1 || isMeta t in
List.for_all p sigma
with UFAIL(_,_)->false
|
