law sorted_head_le_mem
import bend-mathlib@0.8.1.0/list.bend as Listimport Base
import bend-mathlib@0.8.1.0/nat.bend as MNat
1012# The head of a Nat list sorted by Nat.is_le is <= every member of its tail.
1013law sorted_head_le_mem:
1014 for x: Nat
1015 for xs: List<&2, Nat>
1016 for y: Nat
1017 for hs: sorted_by(~Nat, ~Nat.is_le, x <> xs)
1018 for hm: mem(~Nat, ~Nat.is_eq, y, xs)
1019 MNat.le(x, y)