List.mem_append_left: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/list.bend as List
Lines 789-795 of bend-mathlib@0.8.1.0/list.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/list.bend&start_line=789&end_line=795

import Base

# A member of xs is a member of xs ++ ys (Nat lists).
law mem_append_left:
  for xs: List<&2, Nat>
  for ys: List<&2, Nat>
  for x: Nat
  for h: mem(~Nat, ~Nat.is_eq, x, xs)
  mem(~Nat, ~Nat.is_eq, x, List.append(&2, Nat, xs, ys))

Uses (6):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.append
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.is_eq
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/list.bend&name=internal_mem_append_left
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/list.bend&name=mem