fact: Definition oimg (A B : finType) (f : A -> option B) : {set B} := [set b | [exists a, f a == Some b]].
imports: mathcomp(all_ssreflect ssralg ssrnum fingroup finalg perm) mathcomp(zmodp matrix vector order) mathcomp(lra mathcomp_extra Rstruct reals) Reals ssrR realType_ext Reals_ext ssr_ext ssralg_ext f2 fdist proba channel_code channel binary_symmetric_channel hamming pproba