| # s0 ≤ # s, s ⊆ s0, ∃ s1. s0 = s1 ++ a ∧ ¬ a ∈ s1 ⊦ a ∈ s |
# s1 < # s, s ⊆ s1 ++ a ⊦ a ∈ s1, a ∈ s
Used simplifier rules: Size-insert: ⊦ ¬ a ∈ s → #(s ++ a) = # s + 1;% ⊦ m < n → n ≠ 0; (s)%f: ⊦ m < n → n ≠ 0; (forward) from specification nat-basic%c: ⊦ m + n = n + m; from specification nat-basic%a: ⊦ (m + n0) + n1 = m + n0 + n1; from specification nat-basic% ⊦ m + 1 ≤ n ↔ m < n; (s)