exception UnificationFailure of string Lazy.t;;
-module Founif (B : Terms.Blob) = struct
- module Subst = FoSubst (*.Subst(B)*)
+let mem2 a b l =
+ let rec aux found_a found_b = function
+ | x :: tl ->
+ let found_a = found_a || x = a in
+ let found_b = found_b || x = b in
+ if found_a && found_b then true, true
+ else aux found_a found_b tl
+ | [] -> found_a, found_b
+ in
+ aux false false l
+;;
+
+module Founif (B : Orderings.Blob) = struct
+ module Subst = FoSubst
module U = FoUtils.Utils(B)
- let unification vars locked_vars t1 t2 =
+ let unification (* vars *) locked_vars t1 t2 =
let rec occurs_check subst what where =
match where with
| Terms.Var i when i = what -> true
in
match s, t with
| s, t when U.eq_foterm s t -> subst
- | Terms.Var i, Terms.Var j
- when (List.mem i locked_vars) &&(List.mem j locked_vars) ->
- raise
- (UnificationFailure (lazy "Inference.unification.unif"))
- | Terms.Var i, Terms.Var j when (List.mem i locked_vars) ->
- unif subst t s
- | Terms.Var i, Terms.Var j when (i > j) && not (List.mem j locked_vars) ->
- unif subst t s
+ | Terms.Var i, Terms.Var j ->
+ (* TODO: look in locked vars for both i and j at once *)
+ let i_locked, j_locked = mem2 i j locked_vars in
+ if i_locked then
+ if j_locked then
+ raise (UnificationFailure (lazy "Inference.unification.unif"))
+ else
+ Subst.build_subst j s subst
+ else
+ Subst.build_subst i t subst
| Terms.Var i, t when occurs_check subst i t ->
- raise
- (UnificationFailure (lazy "Inference.unification.unif"))
+ raise (UnificationFailure (lazy "Inference.unification.unif"))
| Terms.Var i, t when (List.mem i locked_vars) ->
- raise
- (UnificationFailure (lazy "Inference.unification.unif"))
- | Terms.Var i, t ->
- let subst = Subst.build_subst i t subst in
- subst
- | _, Terms.Var _ -> unif subst t s
+ raise (UnificationFailure (lazy "Inference.unification.unif"))
+ | Terms.Var i, t -> Subst.build_subst i t subst
+ | t, Terms.Var i when occurs_check subst i t ->
+ raise (UnificationFailure (lazy "Inference.unification.unif"))
+ | t, Terms.Var i when (List.mem i locked_vars) ->
+ raise (UnificationFailure (lazy "Inference.unification.unif"))
+ | t, Terms.Var i -> Subst.build_subst i t subst
| Terms.Node l1, Terms.Node l2 -> (
try
List.fold_left2
raise (UnificationFailure (lazy "Inference.unification.unif"))
in
let subst = unif Subst.id_subst t1 t2 in
- let vars = Subst.filter subst vars in
- subst, vars
+ subst
;;
+(* Sets of variables in s and t are assumed to be disjoint *)
let alpha_eq s t =
let rec equiv subst s t =
let s = match s with Terms.Var i -> Subst.lookup i subst | _ -> s
and t = match t with Terms.Var i -> Subst.lookup i subst | _ -> t
-
+
in
match s, t with
- | s, t when U.eq_foterm s t -> subst
- | Terms.Var i, Terms.Var j
- when (not (List.exists (fun (_,k) -> k=t) subst)) ->
+ | s, t when U.eq_foterm s t -> subst
+ | Terms.Var i, Terms.Var j
+ when (not (List.exists (fun (_,k) -> k=t) subst)) ->
let subst = Subst.build_subst i t subst in
subst
- | Terms.Node l1, Terms.Node l2 -> (
+ | Terms.Node l1, Terms.Node l2 -> (
try
List.fold_left2
- (fun subst' s t -> equiv subst' s t)
- subst l1 l2
+ (fun subst' s t -> equiv subst' s t)
+ subst l1 l2
with Invalid_argument _ ->
raise (UnificationFailure (lazy "Inference.unification.unif"))
)
- | _, _ ->
+ | _, _ ->
raise (UnificationFailure (lazy "Inference.unification.unif"))
in
equiv Subst.id_subst s t
;;
+
end