fact: Hypothesis discard_cancel : forall y x, repair y = Some x -> enc (discard x) = x.
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