| i < 0 ⊦ path∃(str, r, r1, st[r0 -- i ', val]) ↔ path∃(str, r, r1, st) |
⊦ path∃(str, r, r0, st) ↔ (∃ refs. refs ≠ [] ∧ refs .first = r ∧ refs .last = r0 ∧ validrefs(str, refs, st[r -- _type] .type, st))
i < 0 ⊦ path∃(str, r, r1, st[r0 -- i ', val]) ↔ (∃ refs. refs ≠ [] ∧ refs .first = r ∧ refs .last = r1 ∧ validrefs(str, refs, st[r -- _type] .type, st))
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st, r1, r, str)]]