| ⊦ count(a, bag0 \ ∅) = (count(a, ∅) < count(a, bag0) ⊃ count(a, bag0) - count(a, ∅);0) |
⊦ count(a, bag0) = (count(a, bag0) ≠ 0 ⊃ count(a, bag0);0)
Used simplifier rules: diff-empty: ⊦ bag0 \ ∅ = bag0;% ⊦ m - 0 = m; (s)% ⊦ 0 < m ↔ m ≠ 0; (s)% ⊦ count(a, ∅) = 0; (s)