def swap_m

bend-collections-laws-math@1.0.0.0 · src/math/random/rand.bend:270

import Base

270def swap_m(-A: Data, xs: List<&2, A>, +i: Nat, +j: Nat, a: Maybe<&2, A>, b: Maybe<&2, A>) -> List<&2, A>:
271  match a b:
272    case Some{x} Some{y}:
273      put(A, put(A, xs, i, y), j, x)
274    case _ _:
275      xs