| st ⊆ st0, cyclic(str, r, st0) ⊦ cyclic(str, r, st), junkref(str, r, st) |
⊦ cyclic(str, r, st) ↔ (∃ refs. dups(refs) ∧ refs .first = r ∧ validrefs(str, refs, st[r -- _type] .type, st))
st ⊆ st0, ∃ refs. dups(refs) ∧ refs .first = r ∧ validrefs(str, refs, st0[r -- _type] .type, st0) ⊦ cyclic(str, r, st), junkref(str, r, st)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st0, r, str)]]