Shuffle.swap_m_occ: def of bend-collections-laws-math@1.0.0.0
Import: import bend-collections-laws-math@1.0.0.0/proofs/math/random/shuffle.bend as Shuffle
Lines 87-94 of bend-collections-laws-math@1.0.0.0/proofs/math/random/shuffle.bend: https://jend.leeeet.dev/read.txt?path=bend-collections-laws-math@1.0.0.0/proofs/math/random/shuffle.bend&start_line=87&end_line=94

import Base
import bend-collections-laws-math@1.0.0.0/src/math/random/rand.bend as R

def swap_m_occ(~A: Data, ~V: Data, ~rel: A -> V -> Bool, +v: V, +xs: List<&2, A>, +i: Nat, +j: Nat, +a: Maybe<&2, A>, +b: Maybe<&2, A>, +ha: {R.nth(A, xs, i) == a : Maybe<&2, A>}, +hb: {R.nth(A, xs, j) == b : Maybe<&2, A>}) -> {occ(~A, ~V, ~rel, v, R.swap_m(A, xs, i, j, a, b)) == occ(~A, ~V, ~rel, v, xs) : Nat}:
  match a b:
    case Some{x} Some{y}:
      swap_some(~A, ~V, ~rel, v, xs, i, j, x, y, ha, hb)
    case None{} _:
      {==}
    case Some{x} None{}:
      {==}

Uses (8):
  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=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-math@1.0.0.0/proofs/math/random/shuffle.bend&name=occ
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-math@1.0.0.0/proofs/math/random/shuffle.bend&name=swap_some
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-math@1.0.0.0/src/math/random/rand.bend&name=nth
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-math@1.0.0.0/src/math/random/rand.bend&name=swap_m