| x + y = a0 ' + x0, a ∈ x, a0 ∈ x ∨ a0 ∈ y ⊦ x + y = [], a0 = x.first |
Used simplifier rules: Nil: ⊦ [] + x = x;%a: ⊦ (x + y) + z = x + y + z;%in-empty: ⊦ ¬ a ∈ [];%c: ⊦ a + x = a ' + x;%a: ⊦ (x + y) + z = x + y + z;%c-06: ⊦ a ' + x = b ' + y ↔ a = b ∧ x = y;%x ≠ [] ⊦ a = x.first ∧ y = x.rest ↔ x = a + y; (elim) Used terms: x, a1, y0