Loop detection: before expanding a haz formula, see whether it is a duplicate
and, if so, delete it.
Recursion detection: transitivity and similar rules, when applied, put the
new formulae at the end of a branch and not at the front (in effect).
signature Thms_sig =
sig
type Thm
val WF_INDUCTION_THM:Thm
val WFREC_COROLLARY :Thm
val CUT_DEF :Thm
val CUT_LEMMA :Thm
val SELECT_AX :Thm
val COND_CONG :Thm
val LET_CONG :Thm
val eqT :Thm
val rev_eq_mp :Thm
val simp_thm :Thm
end;