| n + 1 < # x, a ∈ x ⊦ (x \ a ')[n] = (n < pos(a, x) ⊃ x[n];x[n + 1]), dups(x) |
n + 1 < # x, a ∈ x ⊦ (x \ a ')[n] = (n < pos(a, x) ⊃ x[n];x[n + 1]), x = [], dups(x)
Used simplifier rules: ⊦ # x = 0 ↔ x = []; (s)%f: ⊦ m < n → n ≠ 0; (forward) from specification nat-basic