<div id="comment:0"></div> and also forbid compositions containing zeroes CC: @tscrim @mkoeppe @kwankyu @slel Component: **combinatorics** Author: **Frédéric Chapoton** Branch/Commit: **[`8139c36`](https://github.com/sagemath/sagetrac-mirror/commit/8139c367dba1e9ac88703289feb4910e47b9dc7e)** Reviewer: **Travis Scrimshaw** _Issue created by migration from https://trac.sagemath.org/ticket/34689_