Perm.perm_nil: def of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/perm.bend as Perm
Lines 31-33 of bend-mathlib@0.8.1.0/perm.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/perm.bend&start_line=31&end_line=33

import Base
import bendlib-kernel-list@1.0.0.0/list.bend as K

# The empty list is a permutation of itself.
def perm_nil(-A: Data) -> K.perm(A, Nil{}, Nil{}):
  (Nil{}, {==})

Uses (3):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma
  https://jend.leeeet.dev/definition.txt?path=bendlib-kernel-list@1.0.0.0/list.bend&name=perm