| bag1 ⊆ bag0 ⊦ #(bag0 \ bag1) = # bag0 - # bag1 |
∀ bag0. bag ⊆ bag0 → #(bag0 \ bag) = # bag0 - # bag, bag ++ a ⊆ bag0 ⊦ #(bag0 \ (bag ++ a)) = # bag0 - #(bag ++ a)
Used simplifier rules: diff-empty: ⊦ bag0 \ ∅ = bag0;%size-empty: ⊦ # ∅ = 0;%bag generated by ∅, ++;;%sub-base: ⊦ m - 0 = m; from specification nat