src/Pure/more_unify.ML

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/more_unify.ML	Fri Nov 21 18:14:39 2014 +0100
@@ -0,0 +1,85 @@
+(*  Title:      Pure/more_unify.ML
+    Author:     Makarius
+
+Add-ons to Higher-Order Unification, outside the inference kernel.
+*)
+
+signature UNIFY =
+sig
+  include UNIFY
+  val matchers: Context.generic -> (term * term) list -> Envir.env Seq.seq
+  val matches_list: Context.generic -> term list -> term list -> bool
+end;
+
+structure Unify: UNIFY =
+struct
+
+(*Pattern matching*)
+fun first_order_matchers thy pairs (Envir.Envir {maxidx, tenv, tyenv}) =
+  let val (tyenv', tenv') = fold (Pattern.first_order_match thy) pairs (tyenv, tenv)
+  in Seq.single (Envir.Envir {maxidx = maxidx, tenv = tenv', tyenv = tyenv'}) end
+  handle Pattern.MATCH => Seq.empty;
+
+(*General matching -- keep variables disjoint*)
+fun matchers _ [] = Seq.single (Envir.empty ~1)
+  | matchers context pairs =
+      let
+        val thy = Context.theory_of context;
+
+        val maxidx = fold (Term.maxidx_term o #2) pairs ~1;
+        val offset = maxidx + 1;
+        val pairs' = map (apfst (Logic.incr_indexes ([], offset))) pairs;
+        val maxidx' = fold (fn (t, u) => Term.maxidx_term t #> Term.maxidx_term u) pairs' ~1;
+
+        val pat_tvars = fold (Term.add_tvars o #1) pairs' [];
+        val pat_vars = fold (Term.add_vars o #1) pairs' [];
+
+        val decr_indexesT =
+          Term.map_atyps (fn T as TVar ((x, i), S) =>
+            if i > maxidx then TVar ((x, i - offset), S) else T | T => T);
+        val decr_indexes =
+          Term.map_types decr_indexesT #>
+          Term.map_aterms (fn t as Var ((x, i), T) =>
+            if i > maxidx then Var ((x, i - offset), T) else t | t => t);
+
+        fun norm_tvar env ((x, i), S) =
+          let
+            val tyenv = Envir.type_env env;
+            val T' = Envir.norm_type tyenv (TVar ((x, i), S));
+          in
+            if (case T' of TVar (v, _) => v = (x, i) | _ => false) then NONE
+            else SOME ((x, i - offset), (S, decr_indexesT T'))
+          end;
+
+        fun norm_var env ((x, i), T) =
+          let
+            val tyenv = Envir.type_env env;
+            val T' = Envir.norm_type tyenv T;
+            val t' = Envir.norm_term env (Var ((x, i), T'));
+          in
+            if (case t' of Var (v, _) => v = (x, i) | _ => false) then NONE
+            else SOME ((x, i - offset), (decr_indexesT T', decr_indexes t'))
+          end;
+
+        fun result env =
+          if Envir.above env maxidx then   (* FIXME proper handling of generated vars!? *)
+            SOME (Envir.Envir {maxidx = maxidx,
+              tyenv = Vartab.make (map_filter (norm_tvar env) pat_tvars),
+              tenv = Vartab.make (map_filter (norm_var env) pat_vars)})
+          else NONE;
+
+        val empty = Envir.empty maxidx';
+      in
+        Seq.append
+          (Seq.map_filter result (Unify.smash_unifiers context pairs' empty))
+          (first_order_matchers thy pairs empty)
+      end;
+
+fun matches_list context ps os =
+  length ps = length os andalso is_some (Seq.pull (matchers context (ps ~~ os)));
+
+
+open Unify;
+
+end;
+