| ⊦ (s ++ b) -- a = (s -- a) ++ b, a = b, b ∈ s |
a0 = b ∨ a0 ≠ a ∧ a0 ∈ s ⊦ a = b, b ∈ s, a0 ≠ a ∧ (a0 = b ∨ a0 ∈ s)
Used simplifier rules: Delete: ⊦ a ∈ s -- b ↔ a ≠ b ∧ a ∈ s;% ⊦ a ∈ s ++ b ↔ a = b ∨ a ∈ s; (s)% ⊦ s1 = s2 ↔ (∀ a. a ∈ s1 ↔ a ∈ s2); (s)