law is_empty_append

bend-mathlib@0.8.1.0 · list.bend:1849

import Base

1849# An append is empty exactly when both parts are.
1850law is_empty_append:
1851  for -a: Quant
1852  for -A: Kind(a)
1853  for xs: List<a, A>
1854  for -ys: List<a, A>
1855  {List.is_empty(a, A, List.append(a, A, xs, ys)) == Bool.and(List.is_empty(a, A, xs), List.is_empty(a, A, ys)) : Bool}