fact: Definition o_PI (m m' : M) := fun g : encT A M n => [ffun x => g (tperm m m' x)].
imports: mathcomp(all_ssreflect ssralg ssrnum matrix perm) Reals Lra Classical mathcomp(Rstruct classical_sets) ssrZ ssrR Reals_ext realType_ext logb ssr_ext ssralg_ext bigop_ext fdist proba entropy aep typ_seq joint_typ_seq channel channel_code