diff -r cfc11af6174a -r 8c9278991d9c src/Sequents/modal.ML
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Sequents/modal.ML	Tue Jul 27 19:00:55 1999 +0200
@@ -0,0 +1,93 @@
+(*  Title:      LK/modal.ML
+    ID:         $Id$
+    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
+    Copyright   1992  University of Cambridge
+
+Simple modal reasoner
+*)
+
+
+signature MODAL_PROVER_RULE =
+sig
+    val rewrite_rls      : thm list
+    val safe_rls         : thm list
+    val unsafe_rls       : thm list
+    val bound_rls        : thm list
+    val aside_rls        : thm list
+end;
+
+signature MODAL_PROVER = 
+sig
+    val rule_tac   : thm list -> int ->tactic
+    val step_tac   : int -> tactic
+    val solven_tac : int -> int -> tactic
+    val solve_tac  : int -> tactic
+end;
+
+functor Modal_ProverFun (Modal_Rule: MODAL_PROVER_RULE) : MODAL_PROVER = 
+struct
+local open Modal_Rule
+in 
+
+(*Returns the list of all formulas in the sequent*)
+fun forms_of_seq (Const("SeqO",_) $ P $ u) = P :: forms_of_seq u
+  | forms_of_seq (H $ u) = forms_of_seq u
+  | forms_of_seq _ = [];
+
+(*Tests whether two sequences (left or right sides) could be resolved.
+  seqp is a premise (subgoal), seqc is a conclusion of an object-rule.
+  Assumes each formula in seqc is surrounded by sequence variables
+  -- checks that each concl formula looks like some subgoal formula.*)
+fun could_res (seqp,seqc) =
+      forall (fn Qc => exists (fn Qp => could_unify (Qp,Qc)) 
+                              (forms_of_seq seqp))
+             (forms_of_seq seqc);
+
+(*Tests whether two sequents G|-H could be resolved, comparing each side.*)
+fun could_resolve_seq (prem,conc) =
+  case (prem,conc) of
+      (_ $ Abs(_,_,leftp) $ Abs(_,_,rightp),
+       _ $ Abs(_,_,leftc) $ Abs(_,_,rightc)) =>
+          could_res (leftp,leftc)  andalso  could_res (rightp,rightc)
+    | _ => false;
+
+(*Like filt_resolve_tac, using could_resolve_seq
+  Much faster than resolve_tac when there are many rules.
+  Resolve subgoal i using the rules, unless more than maxr are compatible. *)
+fun filseq_resolve_tac rules maxr = SUBGOAL(fn (prem,i) =>
+  let val rls = filter_thms could_resolve_seq (maxr+1, prem, rules)
+  in  if length rls > maxr  then  no_tac  else resolve_tac rls i
+  end);
+
+fun fresolve_tac rls n = filseq_resolve_tac rls 999 n;
+
+(* NB No back tracking possible with aside rules *)
+
+fun aside_tac n = DETERM(REPEAT (filt_resolve_tac aside_rls 999 n));
+fun rule_tac rls n = fresolve_tac rls n THEN aside_tac n;
+
+val fres_safe_tac = fresolve_tac safe_rls;
+val fres_unsafe_tac = fresolve_tac unsafe_rls THEN' aside_tac;
+val fres_bound_tac = fresolve_tac bound_rls;
+
+fun UPTOGOAL n tf = let fun tac i = if i<n then all_tac
+                                    else tf(i) THEN tac(i-1)
+                    in fn st => tac (nprems_of st) st end;
+
+(* Depth first search bounded by d *)
+fun solven_tac d n state = state |>
+       (if d<0 then no_tac
+        else if (nprems_of state = 0) then all_tac 
+        else (DETERM(fres_safe_tac n) THEN UPTOGOAL n (solven_tac d)) ORELSE
+                 ((fres_unsafe_tac n  THEN UPTOGOAL n (solven_tac d)) APPEND
+                   (fres_bound_tac n  THEN UPTOGOAL n (solven_tac (d-1)))));
+
+fun solve_tac d = rewrite_goals_tac rewrite_rls THEN solven_tac d 1;
+
+fun step_tac n = 
+    COND (has_fewer_prems 1) all_tac 
+         (DETERM(fres_safe_tac n) ORELSE 
+	  (fres_unsafe_tac n APPEND fres_bound_tac n));
+
+end;
+end;