| ∀ a. x0 -1l a = [] → x0 = [] ∨ x0 = a ', (a0 + x0) -1l a = [] ⊦ a0 + x0 = [], a0 + x0 = a ' |
(a0 ' + x0) -1l a = [], ∀ a. x0 -1l a = [] → x0 = [] ∨ x0 = a ' ⊦ a0 ' + x0 = a '
Used simplifier rules: a: ⊦ (x + y) + z = x + y + z; from specification list%e-01: ⊦ a ' + x ≠ []; from specification list%c: ⊦ a + x = a ' + x; from specification list