src/Pure/thm_deps.ML

   val all_oracles: thm list -> Proofterm.oracle list
   val has_skip_proof: thm list -> bool
   val pretty_thm_oracles: Proof.context -> thm list -> Pretty.T
   val thm_deps: theory -> thm list -> (Proofterm.thm_id * Thm_Name.T) list
   val pretty_thm_deps: theory -> thm list -> Pretty.T
+  val proof_boxes: (Proofterm.thm_id -> bool) -> thm -> Proofterm.thm_id list
   val unused_thms_cmd: theory list * theory list -> (string * thm) list
 end;
 
 structure Thm_Deps: THM_DEPS =
 struct

       |> map (fn ((marks, xname), i) =>
           Pretty.item [Pretty.marks_str (marks, Thm_Name.print (xname, i))]);
   in Pretty.big_list ("dependencies: " ^ string_of_int (length items)) items end;
 
 
+(* proof boxes: undefined PThm nodes *)
+
+fun proof_boxes defined thm =
+  let
+    fun boxes (i, thm_node) res =
+      let val thm_id = Proofterm.thm_id (i, thm_node) in
+        if defined thm_id orelse Inttab.defined res i then res
+        else
+          Inttab.update (i, thm_id) res
+          |> fold boxes (Proofterm.thm_node_thms thm_node)
+      end;
+  in Inttab.fold_rev (cons o #2) (fold boxes (Thm.thm_deps thm) Inttab.empty) [] end;
+
+
 (* unused_thms_cmd *)
 
 fun unused_thms_cmd (base_thys, thys) =
   let
     fun add_fact transfer space (name, ths) =