# Commit 2022-11-14 15:10 ed98c07f

View on Github →feat(algebraic_topology/dold_kan): a few basic lemmas and a property of P_infty (#17538)
This PR introduces some very basic lemmas for the complement projection `Q`

of `P`

. We also obtain the lemma `ι_summand_comp_P_infty_eq_zero`

which states that in a given degree, `P_infty`

vanishes on all the summands of a split simplicial object except one.