fact: Definition shell := [set tb : n.-tuple B | [forall a, [forall b, N(a, b |ta, tb) == (JType.f V) a b]]].
imports: mathcomp(all_ssreflect ssralg ssrnum fingroup perm) Reals mathcomp(Rstruct) ssrR Reals_ext realType_ext ssr_ext ssralg_ext logb fdist entropy num_occ channel types