def swap_at

bendlib-kernel-list@1.0.0.0 · list.bend:17

import Base

17# Swap positions i and i+1.
18def swap_at(-A: Data, +i: Nat, xs: List<&2, A>) -> List<&2, A>:
19  match i:
20    case 0n:
21      swap_head(A, xs)
22    case 1n+p:
23      match xs:
24        case Nil{}:
25          Nil{}
26        case +x <> t:
27          x <> swap_at(A, p, t)