| ∀ a, bag1. count(a, bag ∪ bag1) = count(a, bag) + count(a, bag1) ⊦ count(a, (bag ++ a0) ∪ bag1) = count(a, bag ++ a0) + count(a, bag1) |
∀ a, bag1. count(a, bag ∪ bag1) = count(a, bag) + count(a, bag1) ⊦ count(a, (bag ∪ bag1) ++ a0) = count(a, bag ++ a0) + count(a, bag1)
Used simplifier rules: union-rec: ⊦ (bag0 ++ a) ∪ bag1 = (bag0 ∪ bag1) ++ a;