flowing

flowing($pdl) — no-op stub, returns self. flowing($pdl) — enable forward-flow dataflow on this pdl. Sets PDL_DATAFLOW_F on the state flags. Upstream Core.pm semantics: trans created from this pdl retain their link so parent changes cascade to children.

NOTE (Phase A status): we mark the flag and the slice/affine forward-flow path works (set → pdl_mark_children_dirty). Full trans-retention for non-affine transforms (e.g. $a + $a) is the remaining Phase A work — without it, $pb = $pa + $pa; $pa ->set(...) does not refresh $pb since the + trans was freed after its one-shot execution.