# Commit 2022-08-10 10:23 3dbd6809

View on Github →feat(algebraic_topology/dold_kan): construction of an idempotent endomorphism (#15950)
In this PR, we pass to the limit in order to obtain the endomorphism `P_infty : K[X] ⟶ K[X]`

of the alternating face map complex. In the case of abelian categories, it shall be the projection on the normalized subcomplex, with kernel the degenerate subcomplex.