proposition: Lemma fgoppE g k : (fgopp g)@_k = - g@_k.
proof: Proof. by rewrite mcoeffE; case: msuppP; rewrite ?oppr0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap