| a ∈ bag ⊦ (a0 = a ⊃ 1;0) + count(a0, bag -- a) = count(a0, bag) |
a ∈ bag ⊦ (a0 = a ⊃ 1;0) + (count(a0, bag) - (a0 = a ∧ count(a, bag) ≠ 0 ⊃ 1;0)) = count(a0, bag)
Used simplifier rules: count-del: ⊦ count(a, bag -- b) = count(a, bag) - (a = b ∧ count(a, bag) ≠ 0 ⊃ 1;0);