law length_tail_sym

bend-mathlib@0.8.1.0 · list.bend:2669

import Base

2669# The tail is one shorter than the list, or empty: length (tail xs) = length xs - 1, reversed to rewrite toward the simple side.
2670law length_tail_sym:
2671  for -a: Quant
2672  for -A: Kind(a)
2673  for xs: List<a, A>
2674  {Nat.sub(List.length(a, A, xs), 1n) == List.length(a, A, List.tail(a, A, xs)) : Nat}