| # y + 1 = n0 + n, ∀ x0, n0, n. # x0 < #(y + a ') → # x0 = n0 + n → # butlastn(n, x0) = n0 ⊦ # butlastn(n -1, y) = n0, n = 0 |
# y + 1 = n0 + n, ∀ x0, n0, n. # x0 < #(y + a ') → # x0 = n0 + n → # butlastn(n, x0) = n0 ⊦ # butlastn(n - 1, y) = n0, n = 0
Used simplifier rules: ⊦ n -1 = n - 1; (s)