| # x0 + # z = # x1 + # x2, # x2 < n, # x1 + n < # x0, ∀ n0. n0 < # x1 + # x2 → (x0 + z)[n0] = (x1 + x2)[n0] ⊦ x0 = [] |
⊦ m < n ↔ (∃ m0. m + m0 = n ∧ m0 ≠ 0)
# x0 + # z = # x1 + # x2, # x2 < n, ∀ n0. n0 < # x1 + # x2 → (x0 + z)[n0] = (x1 + x2)[n0], ∃ m0. (# x1 + n) + m0 = # x0 ∧ m0 ≠ 0 ⊦ x0 = []
Used terms: # x0, # x1 + n