law length_tail

bend-mathlib@0.8.1.0 · list.bend:1274

import Base

1274# The tail is one shorter than the list, or empty: length (tail xs) = length xs - 1.
1275law length_tail:
1276  for -a: Quant
1277  for -A: Kind(a)
1278  for xs: List<a, A>
1279  {List.length(a, A, List.tail(a, A, xs)) == Nat.sub(List.length(a, A, xs), 1n) : Nat}