def sp.join_split
import bend-osdev-cbc@0.1.0.0/PROOF.bend as PROOFimport Base
import bend-osdev-bytes@0.1.1.0/bytes.bend as B
import bend-osdev-mode-core@0.1.0.0/mode_core.bend as M
import bend-osdev-mode-core@0.1.0.0/LAWS.bend as CoreL
28def sp.join_split(ys: List<&2, U32>) -> {M.cm.join_onto(M.cm.split.blocks(M.cm.split(B.mask(ys))), M.cm.split.tail(M.cm.split(B.mask(ys)))) == B.mask(ys) : List<&2, U32>}:
29 CoreL.join_split(ys)