| #(s0 \ s) = # s0 - # s, a ∈ s0, a0 ∈ s0, ∀ a0. a0 ∈ s ++ a → a0 ∈ s0 ⊦ # s0 - # s - 1 = # s0 - # s + 1, a ∈ s |
#(s0 \ s) = # s0 - # s, a ∈ s0, a0 ∈ s0, ∀ a0. a0 ∈ s ++ a → a0 ∈ s0 ⊦ # s ≤ # s0, # s0 - # s - 1 = # s0 - # s + 1, a ∈ s
# s0 = n0 + # s ∧ # s ≤ # s0, #(s0 \ s) = n0, a ∈ s0, a0 ∈ s0, ∀ a0. a0 ∈ s ++ a → a0 ∈ s0 ⊦ n0 - 1 = # s0 - # s + 1, a ∈ s
Used simplifier rules: n ≤ m ⊦ n0 = m - n ↔ m = n0 + n; (elim) Used terms: # s0, # s, n