| m ≤ # x + # y, # x ≤ m ⊦ firstn(m, x + y) = x + firstn(m - # x, y) |
m ≤ # x + # y, # x ≤ m ⊦ firstn(m, x + y) = x + firstn(m - # x, y)
Used simplifier rules: c: ⊦ m + n = n + m; from specification nat-basic%a: ⊦ (m + n0) + n1 = m + n0 + n1; from specification nat-basic% ⊦ m ≤ m + n; (s)%let: ⊦ n ≤ n0 ∧ n0 ≤ n1 → n ≤ n1; (forward) from specification nat