Theory.scrub

In the following, we define a concrete type and examine the current theory segment to see what consequences of this definition have been stored there. Then we delete the type, which turns all those consequences into garbage. An query, like current_theorems, shows that this garbage is not collected automatically. A manual invocation of scrub is necessary to show the true state of play.

   - Hol_datatype `foo = A | B of 'a`;
   <<HOL message: Defined type: "foo">>
   > val it = () : unit
   
   - current_theorems();
   > val it =
       [("foo_induction", |- !P. P A /\ (!a. P (B a)) ==> !f. P f),
        ("foo_Axiom", |- !f0 f1. ?fn. (fn A = f0) /\ !a. fn (B a) = f1 a),
        ("foo_nchotomy", |- !f. (f = A) \/ ?a. f = B a),
        ("foo_case_cong",
         |- !M M' v f.
              (M = M') /\ ((M' = A) ==> (v = v')) /\
              (!a. (M' = B a) ==> (f a = f' a)) ==>
              (case v f M = case v' f' M')), 
        ("foo_distinct", |- !a. ~(A = B a)),
        ("foo_11", |- !a a'. (B a = B a') = (a = a'))] : (string * thm) list
   
   - delete_type "foo";
   > val it = () : unit
   
   - current_theorems();
   > val it =
       [("foo_induction", |- !P. P A /\ (!a. P (B a)) ==> !f. P f),
        ("foo_Axiom", |- !f0 f1. ?fn. (fn A = f0) /\ !a. fn (B a) = f1 a),
        ("foo_nchotomy", |- !f. (f = A) \/ ?a. f = B a),
        ("foo_case_cong",
         |- !M M' v f.
              (M = M') /\ ((M' = A) ==> (v = v')) /\
              (!a. (M' = B a) ==> (f a = f' a)) ==>
              (case v f M = case v' f' M')), 
        ("foo_distinct", |- !a. ~(A = B a)),
        ("foo_11", |- !a a'. (B a = B a') = (a = a'))] : (string * thm) list
   
   - scrub();
   > val it = () : unit

   - current_theorems();
   > val it = [] : (string * thm) list