| ⊦ # x < # x1 → (x + x0 = x1 + x2 ↔ (∃ y. x1 = x + y ∧ x0 = y + x2)) |
x + x0 = x1 + x2, # x < # x1 ⊦ x1 = [], ∃ y. x1 = x + y ∧ x0 = y + x2
Used simplifier rules: a: ⊦ (x + y) + z = x + y + z;%l: ⊦ # x = 0 ↔ x = []; from specification list-data%f: ⊦ m < n → n ≠ 0; (forward) from specification nat-basic1