Limit the number of results returned by auto_solves.

--- a/src/Pure/Tools/find_theorems.ML	Sun Mar 29 19:48:35 2009 +0200
+++ b/src/Pure/Tools/find_theorems.ML	Mon Mar 30 12:25:52 2009 +1100
@@ -11,8 +11,8 @@
     Pattern of 'term
   val tac_limit: int ref
   val limit: int ref
-  val find_theorems: Proof.context -> thm option -> bool ->
-    (bool * string criterion) list -> (Facts.ref * thm) list
+  val find_theorems: Proof.context -> thm option -> int option -> bool ->
+    (bool * string criterion) list -> int option * (Facts.ref * thm) list
   val pretty_thm: Proof.context -> Facts.ref * thm -> Pretty.T
   val print_theorems: Proof.context -> thm option -> int option -> bool ->
     (bool * string criterion) list -> unit
@@ -254,12 +254,13 @@
           in app (opt_add r r', consts', fs) end;
   in app end;
 
+ 
 in
 
 fun filter_criterion ctxt opt_goal (b, c) =
   (if b then I else (apfst opt_not)) o filter_crit ctxt opt_goal c;
 
-fun all_filters filters thms =
+fun sorted_filter filters thms =
   let
     fun eval_filters thm = app_filters thm (SOME (0, 0), NONE, filters);
 
@@ -270,6 +271,15 @@
       prod_ord int_ord int_ord ((p1, s1), (p0, s0));
   in map_filter eval_filters thms |> sort thm_ord |> map #2 end;
 
+fun lazy_filter filters = let
+    fun lazy_match thms = Seq.make (fn () => first_match thms)
+
+    and first_match [] = NONE
+      | first_match (thm::thms) =
+          case app_filters thm (SOME (0, 0), NONE, filters) of
+            NONE => first_match thms
+          | SOME (_, t) => SOME (t, lazy_match thms);
+  in lazy_match end;
 end;
 
 
@@ -334,7 +344,7 @@
 
 val limit = ref 40;
 
-fun find_theorems ctxt opt_goal rem_dups raw_criteria =
+fun find_theorems ctxt opt_goal opt_limit rem_dups raw_criteria =
   let
     val assms = ProofContext.get_fact ctxt (Facts.named "local.assms")
                 handle ERROR _ => [];
@@ -344,13 +354,25 @@
     val criteria = map (apsnd (read_criterion ctxt)) raw_criteria;
     val filters = map (filter_criterion ctxt opt_goal') criteria;
 
-    val raw_matches = all_filters filters (all_facts_of ctxt);
+    fun find_all facts =
+      let
+        val raw_matches = sorted_filter filters facts;
+
+        val matches =
+          if rem_dups
+          then rem_thm_dups (nicer_shortest ctxt) raw_matches
+          else raw_matches;
 
-    val matches =
-      if rem_dups
-      then rem_thm_dups (nicer_shortest ctxt) raw_matches
-      else raw_matches;
-  in matches end;
+        val len = length matches;
+        val lim = the_default (! limit) opt_limit;
+      in (SOME len, Library.drop (len - lim, matches)) end;
+
+    val find =
+      if rem_dups orelse is_none opt_limit
+      then find_all
+      else pair NONE o Seq.list_of o Seq.take (the opt_limit) o lazy_filter filters
+
+  in find (all_facts_of ctxt) end;
 
 
 fun pretty_thm ctxt (thmref, thm) = Pretty.block
@@ -362,11 +384,16 @@
     val start = start_timing ();
 
     val criteria = map (apsnd (read_criterion ctxt)) raw_criteria;
-    val matches = find_theorems ctxt opt_goal rem_dups raw_criteria;
-
-    val len = length matches;
-    val lim = the_default (! limit) opt_limit;
-    val thms = Library.drop (len - lim, matches);
+    val (foundo, thms) = find_theorems ctxt opt_goal opt_limit rem_dups raw_criteria;
+    val returned = length thms;
+    
+    val tally_msg =
+      case foundo of
+        NONE => "displaying " ^ string_of_int returned ^ " theorems"
+      | SOME found => "found " ^ string_of_int found ^ " theorems" ^
+                      (if returned < found
+                       then " (" ^ string_of_int returned ^ " displayed)"
+                       else "");
 
     val end_msg = " in " ^ Time.toString (#all (end_timing start)) ^ " secs";
   in
@@ -374,16 +401,12 @@
         :: Pretty.str "" ::
      (if null thms then [Pretty.str ("nothing found" ^ end_msg)]
       else
-        [Pretty.str ("found " ^ string_of_int len ^ " theorems" ^
-          (if len <= lim then ""
-           else " (" ^ string_of_int lim ^ " displayed)")
-           ^ end_msg ^ ":"), Pretty.str ""] @
+        [Pretty.str (tally_msg ^ end_msg ^ ":"), Pretty.str ""] @
         map (pretty_thm ctxt) thms)
     |> Pretty.chunks |> Pretty.writeln
   end;
 
 
-
 (** command syntax **)
 
 fun find_theorems_cmd ((opt_lim, rem_dups), spec) =

--- a/src/Tools/auto_solve.ML	Sun Mar 29 19:48:35 2009 +0200
+++ b/src/Tools/auto_solve.ML	Mon Mar 30 12:25:52 2009 +1100
@@ -13,6 +13,7 @@
 sig
   val auto : bool ref
   val auto_time_limit : int ref
+  val limit : int ref
 
   val seek_solution : bool -> Proof.state -> Proof.state
 end;
@@ -22,6 +23,7 @@
 
 val auto = ref false;
 val auto_time_limit = ref 2500;
+val limit = ref 5;
 
 fun seek_solution int state =
   let
@@ -34,9 +36,9 @@
         handle TERM _ => t::conj_to_list ts;
 
     val crits = [(true, FindTheorems.Solves)];
-    fun find g = (NONE, FindTheorems.find_theorems ctxt g true crits);
-    fun find_cterm g = (SOME g, FindTheorems.find_theorems ctxt
-                                  (SOME (Goal.init g)) true crits);
+    fun find g = (NONE, snd (FindTheorems.find_theorems ctxt g (SOME (!limit)) false crits));
+    fun find_cterm g = (SOME g, snd (FindTheorems.find_theorems ctxt
+                                      (SOME (Goal.init g)) (SOME (!limit)) false crits));
 
     fun prt_result (goal, results) =
       let