def swap_occ

bend-collections-laws-math@1.0.0.0 · proofs/math/random/shuffle.bend:96

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

96# THEOREM: a swap keeps every count
97def swap_occ(~A: Data, ~V: Data, ~rel: A -> V -> Bool, +v: V, +xs: List<&2, A>, +i: Nat, +j: Nat) -> {occ(~A, ~V, ~rel, v, R.swap(A, xs, i, j)) == occ(~A, ~V, ~rel, v, xs) : Nat}:
98  swap_m_occ(~A, ~V, ~rel, v, xs, i, j, R.nth(A, xs, i), R.nth(A, xs, j), {==}, {==})