| H[r1] = a × null, ((lls(r0, r1, x1) * lls(r1, null, x0) * P))(H) ⊦ r1 = null, x0 = [], x1 + x0 ≠ [] ∧ (∃ y. x1 + x0 = y + a ' ∧ ((lls(r0, r1, y) * r1 => a × null * P))(H)) |
H[r1] = a × null, ((lls(r0, r1, x1) * lls(r1, null, x0) * P))(H) ⊦ x1 + x0 = [], r1 = null, x0 = [], ∃ y. x1 + x0 = y + a ' ∧ ((lls(r0, r1, y) * r1 => a × null * P))(H)
Used simplifier rules: a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ x + y = [] ↔ x = [] ∧ y = []; (as)