| m ≠ 0, (r ' + x1)[m] = x2 .last, (r ' + x1)[# x2] = x2 .last, path(r ' + x2, H), reachable-n(H, # x2, r, x2 .last), # x2 < m, # x2 < # x1, m ≤ # x1, path(r ' + x1, H) ⊦ x1 = [], x2 = [], ∃ x. path(x, H) ∧ hd x = r ∧ x .last = x2 .last ∧ # x = m + 1 |
(r ' + x1)[m] = x2 .last, (r ' + x1)[# x2] = x2 .last, path(r ' + x2, H), reachable-n(H, # x2, r, x2 .last), # x2 < m, # x2 < # x1, m ≤ # x1, path(r ' + x1, H) ⊦ x1 = [], x2 = [], ∃ x. path(x, H) ∧ hd x = r ∧ x .last = x2 .last ∧ # x = m + 1
[[CONCRETESIMPRULES : ([CSIMPSEQ : ⊦ m < n → n ≠ 0])]]