fact: Definition msym (s : 'S_n) p : {mpoly R[n]} := mmap (@mpolyC n R) (fun i => 'X_(s i)) p.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(order fingroup perm ssralg zmodp poly ssrint) mathcomp(matrix vector) mathcomp(bigenough) ssrcomplements freeg