| ∀ a, bag0. count(a, bag0 \ bag) = (count(a, bag) < count(a, bag0) ⊃ count(a, bag0) - count(a, bag);0) ⊦ count(a, bag0 \ (bag ++ a0)) = (count(a, bag ++ a0) < count(a, bag0) ⊃ count(a, bag0) - count(a, bag ++ a0);0) |
∀ a, bag0. count(a, bag0 \ bag) = (count(a, bag) < count(a, bag0) ⊃ count(a, bag0) - count(a, bag);0) ⊦ count(a, (bag0 -- a0) \ bag) = (count(a, bag ++ a0) < count(a, bag0) ⊃ count(a, bag0) - count(a, bag ++ a0);0)
Used simplifier rules: diff-rec: ⊦ bag0 \ (bag1 ++ a) = (bag0 -- a) \ bag1;