# Commit 2022-10-06 10:46 a87fad7b

View on Github →feat(counterexamples/zero_divisors_in_add_monoid_algebras + data/finsupp/lex): add a counterexample (#16236)
This PR describes a counterexample to a possible weakening of lemmas `finsupp.lex.covariant_class_le_left`

and its analogue
`finsupp.lex.covariant_class_le_right`

: assuming only monotonicity of addition, instead of strict monotonicity would not be strong enough to prove monotonicity of addition for `finsupp`

s.
See also this Zulip discussion for related material.