| unchanged(str, r, st, st1), junkref(str, r, st1) ⊦ junkref(str, r, st) |
⊦ junkref(str, r, st) ↔ (∃ refs. refs ≠ [] ∧ refs .first = r ∧ junkrefs(str, refs, st[r -- _type] .type, st))
unchanged(str, r, st, st1), ∃ refs. refs ≠ [] ∧ refs .first = r ∧ junkrefs(str, refs, st1[r -- _type] .type, st1) ⊦ junkref(str, r, st)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st1, r, str)]]