From 03cebcaaba3ec9f379b37659e8fc5556c6a9a1b6 Mon Sep 17 00:00:00 2001
From: Cyril Cohen
Date: Tue, 8 Sep 2020 16:37:34 +0200
Subject: Adding matrix commutation and its theory

---
 mathcomp/algebra/mxpoly.v | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

(limited to 'mathcomp/algebra/mxpoly.v')

diff --git a/mathcomp/algebra/mxpoly.v b/mathcomp/algebra/mxpoly.v
index 24de1bc..79a28bf 100644
--- a/mathcomp/algebra/mxpoly.v
+++ b/mathcomp/algebra/mxpoly.v
@@ -271,7 +271,7 @@ Local Notation n := n'.+1.
 Variable A : 'M[R]_n.
 Implicit Types p q : {poly R}.
 
-Definition horner_mx := horner_morph (fun a => scalar_mx_comm a A).
+Definition horner_mx := horner_morph (comm_mxC^~ A).
 Canonical horner_mx_additive := [additive of horner_mx].
 Canonical horner_mx_rmorphism := [rmorphism of horner_mx].
 
@@ -939,6 +939,20 @@ Proof. by rewrite /eigenpoly -map_kermxpoly map_mx_eq0. Qed.
 
 End MapKermxPoly.
 
+Section CommmxPoly.
+
+Lemma comm_mx_horner (R : comRingType) (n' : nat) (A B : 'M[R]_n'.+1)
+  (p : {poly R}) : comm_mx A B -> comm_mx A (horner_mx B p).
+Proof.
+by move=> fg; apply: commr_horner => // i; rewrite coef_map; apply/commCmx.
+Qed.
+
+Lemma horner_mxC (R : comRingType) (n' : nat) (A : 'M_n'.+1) (p q : {poly R}) :
+  GRing.comm (horner_mx A p) (horner_mx A p).
+Proof. exact/comm_mx_horner/comm_mx_sym/comm_mx_horner. Qed.
+
+End CommmxPoly.
+
 Section IntegralOverRing.
 
 Definition integralOver (R K : ringType) (RtoK : R -> K) (z : K) :=
-- 
cgit v1.2.3