| x + a ' + z = y + b ' + y0 ⊦ b ∈ x, a ∈ y, a = b ∧ x = y ∧ z = y0 |
∀ a, z, y, b, y0. x0 + a ' + z = y + b ' + y0 → b ∈ x0 ∨ a ∈ y ∨ a = b ∧ x0 = y ∧ z = y0, (a0 + x0) + a ' + z = y + b ' + y0 ⊦ b ∈ a0 + x0, a ∈ y, a = b ∧ a0 + x0 = y ∧ z = y0
Used simplifier rules: Nil: ⊦ [] + x = x;%a: ⊦ (x + y) + z = x + y + z;%inapp-02: ⊦ ¬ a ∈ y → (y + c ' + z = a ' + z0 ↔ y = [] ∧ c = a ∧ z = z0);%in-empty: ⊦ ¬ a ∈ [];%list freely generated by [], +;;