| ∀ a. dups(x0 + a ') ↔ a ∈ x0 ∨ dups(x0) ⊦ dups((a0 + x0) + a ') ↔ a ∈ a0 + x0 ∨ dups(a0 + x0) |
∀ a. dups(x0 + a ') ↔ a ∈ x0 ∨ dups(x0) ⊦ a0 = a ∨ dups(x0 + a ') ↔ a = a0 ∨ a ∈ x0 ∨ dups(x0), a0 ∈ x0
Used simplifier rules: rec: ⊦ dups(a ' + x) ↔ a ∈ x ∨ dups(x);% ⊦ a ∈ b ' ↔ a = b; (s)% ⊦ a ∈ x + y ↔ a ∈ x ∨ a ∈ y; (s)%a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ a + x = a ' + x; (s)