fact: Definition enc_pre_img (P : P_ n ( A )) := [set m | tuple_of_row (enc c m) \in T_{P}].
imports: mathcomp(all_ssreflect ssralg ssrnum perm) mathcomp(matrix) mathcomp(Rstruct) Reals ssrR Reals_ext realType_ext ssr_ext ssralg_ext logb fdist proba entropy num_occ channel_code channel typ_seq