def hcat
import bendtorch@1.3.0.0/main.bend as Bendtorchimport Base
2725# the two halves back as one list, in order (what the laws attn_par_fwd and attn_par_bwd compare the trees with)
2726def hcat(-A: Type, h: Halves<A>) -> List<&1, A>:
2727 match h:
2728 case Halves{l, r}:
2729 List.append(&1, A, l, r)