| validrefs(str, r ' + refs1, st[r -- _type] .type, st), r ∈ refs1 ⊦ refs1 = [], r = refs1 .last, dups(refs1), ∃ refs. refs ≠ [] ∧ refs .first = r ∧ refs .last = refs1 .last ∧ ¬ dups(refs) ∧ validrefs(str, refs, st[refs .first -- _type] .type, st) |
⊦ r ∈ refs ↔ (∃ refs0, refs1. refs = refs0 + (r + refs1))
validrefs(str, r ' + refs1, st[r -- _type] .type, st), ∃ refs0, refs2. refs1 = refs0 + (r + refs2) ⊦ refs1 = [], r = refs1 .last, dups(refs1), ∃ refs. refs ≠ [] ∧ refs .first = r ∧ refs .last = refs1 .last ∧ ¬ dups(refs) ∧ validrefs(str, refs, st[refs .first -- _type] .type, st)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (refs1, r)]]