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