src/Sequents/modal.ML
 author wenzelm Mon Mar 19 21:10:33 2012 +0100 (2012-03-19) changeset 47022 8eac39af4ec0 parent 41449 7339f0e7c513 child 54742 7a86358a3c0b permissions -rw-r--r--
moved some legacy stuff;
1 (*  Title:      Sequents/modal.ML
2     Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
3     Copyright   1992  University of Cambridge
5 Simple modal reasoner.
6 *)
8 signature MODAL_PROVER_RULE =
9 sig
10     val rewrite_rls      : thm list
11     val safe_rls         : thm list
12     val unsafe_rls       : thm list
13     val bound_rls        : thm list
14     val aside_rls        : thm list
15 end;
17 signature MODAL_PROVER =
18 sig
19     val rule_tac   : thm list -> int ->tactic
20     val step_tac   : int -> tactic
21     val solven_tac : int -> int -> tactic
22     val solve_tac  : int -> tactic
23 end;
25 functor Modal_ProverFun (Modal_Rule: MODAL_PROVER_RULE) : MODAL_PROVER =
26 struct
28 (*Returns the list of all formulas in the sequent*)
29 fun forms_of_seq (Const(@{const_name SeqO'},_) \$ P \$ u) = P :: forms_of_seq u
30   | forms_of_seq (H \$ u) = forms_of_seq u
31   | forms_of_seq _ = [];
33 (*Tests whether two sequences (left or right sides) could be resolved.
34   seqp is a premise (subgoal), seqc is a conclusion of an object-rule.
35   Assumes each formula in seqc is surrounded by sequence variables
36   -- checks that each concl formula looks like some subgoal formula.*)
37 fun could_res (seqp,seqc) =
38       forall (fn Qc => exists (fn Qp => Term.could_unify (Qp,Qc))
39                               (forms_of_seq seqp))
40              (forms_of_seq seqc);
42 (*Tests whether two sequents G|-H could be resolved, comparing each side.*)
43 fun could_resolve_seq (prem,conc) =
44   case (prem,conc) of
45       (_ \$ Abs(_,_,leftp) \$ Abs(_,_,rightp),
46        _ \$ Abs(_,_,leftc) \$ Abs(_,_,rightc)) =>
47           could_res (leftp,leftc)  andalso  could_res (rightp,rightc)
48     | _ => false;
50 (*Like filt_resolve_tac, using could_resolve_seq
51   Much faster than resolve_tac when there are many rules.
52   Resolve subgoal i using the rules, unless more than maxr are compatible. *)
53 fun filseq_resolve_tac rules maxr = SUBGOAL(fn (prem,i) =>
54   let val rls = filter_thms could_resolve_seq (maxr+1, prem, rules)
55   in  if length rls > maxr  then  no_tac  else resolve_tac rls i
56   end);
58 fun fresolve_tac rls n = filseq_resolve_tac rls 999 n;
60 (* NB No back tracking possible with aside rules *)
62 fun aside_tac n = DETERM(REPEAT (filt_resolve_tac Modal_Rule.aside_rls 999 n));
63 fun rule_tac rls n = fresolve_tac rls n THEN aside_tac n;
65 val fres_safe_tac = fresolve_tac Modal_Rule.safe_rls;
66 val fres_unsafe_tac = fresolve_tac Modal_Rule.unsafe_rls THEN' aside_tac;
67 val fres_bound_tac = fresolve_tac Modal_Rule.bound_rls;
69 fun UPTOGOAL n tf = let fun tac i = if i<n then all_tac
70                                     else tf(i) THEN tac(i-1)
71                     in fn st => tac (nprems_of st) st end;
73 (* Depth first search bounded by d *)
74 fun solven_tac d n state = state |>
75        (if d<0 then no_tac
76         else if (nprems_of state = 0) then all_tac
77         else (DETERM(fres_safe_tac n) THEN UPTOGOAL n (solven_tac d)) ORELSE
78                  ((fres_unsafe_tac n  THEN UPTOGOAL n (solven_tac d)) APPEND
79                    (fres_bound_tac n  THEN UPTOGOAL n (solven_tac (d-1)))));
81 fun solve_tac d = rewrite_goals_tac Modal_Rule.rewrite_rls THEN solven_tac d 1;
83 fun step_tac n =
84     COND (has_fewer_prems 1) all_tac
85          (DETERM(fres_safe_tac n) ORELSE
86           (fres_unsafe_tac n APPEND fres_bound_tac n));
88 end;