x -1l a = mklist(a, n0), a ∈ x ⊦ x.head = a, x = a ' + mklist(a, n0), x = []
Used simplifier rules: ⊦ ¬ a ∈ []; (s)% ⊦ mklist(a, m) = [] ↔ m = 0; (s)% ⊦ [] -1l a = []; (s)