Perm.insert_by_perm: def of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/perm.bend as Perm
Lines 90-96 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=90&end_line=96

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

# Inserting x into xs permutes x <> xs.
def insert_by_perm(~A: Data, ~le: A -> A -> Bool, +x: A, +xs: List<&2, A>) -> K.perm(A, x <> xs, insert_by(~A, ~le, x, xs)):
  match xs:
    case Nil{}:
      perm_refl(A, x <> Nil{})
    case +y <> t:
      internal_ins_pick(A, le(x, y), x, y, t, insert_by(~A, ~le, x, t), insert_by_perm(~A, ~le, x, t))

Uses (6):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/perm.bend&name=insert_by
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/perm.bend&name=internal_ins_pick
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/perm.bend&name=perm_refl
  https://jend.leeeet.dev/definition.txt?path=bendlib-kernel-list@1.0.0.0/list.bend&name=perm