| # x0 = # x1 ⊦ # prefixn(n, x0) = # prefixn(n, x1) ↔ true |
⊦ prefixn(n, x) = (n ≤ # x ⊃ firstn(n, x);x)
# x0 = # x1 ⊦ # (n ≤ # x1 ⊃ firstn(n, x0);x0) = # (n ≤ # x1 ⊃ firstn(n, x1);x1)
Used simplifier rules: prefixn: ⊦ prefixn(n, x) = (n ≤ # x ⊃ firstn(n, x);x);