fact: Definition f (x : 'rV[A]_n) := [ffun y : 'rV[B]_n => (\prod_(i < n) W `(y ``_ i | x ``_ i))].
imports: mathcomp(all_ssreflect all_algebra) Reals mathcomp(Rstruct) ssrR Reals_ext logb ssr_ext ssralg_ext bigop_ext fdist proba entropy jfdist_cond