| a ∈ bag ⊦ 1 + (count(a, bag) - (count(a, bag) ≠ 0 ⊃ 1;0)) = count(a, bag) |
count(a, bag) = 0, a ∈ bag ⊦ 1 + (count(a, bag) - 0) = count(a, bag)
Used simplifier rules: ⊦ m ≤ n ↔ ¬ n < m; (ss)% ⊦ m < 1 ↔ m = 0; (s)%n ≤ m ⊦ (m - n) + n0 = n1 ↔ m + n0 = n + n1; (s)%c: ⊦ m + n = n + m; from specification nat-basic%a: ⊦ (m + n0) + n1 = m + n0 + n1; from specification nat-basic