fact: Definition pr_eq (X : {RV P -> A}) (a : A) := locked (Pr P (finset (X @^-1 a))).
imports: mathcomp(all_ssreflect ssralg ssrnum matrix) mathcomp(Rstruct reals) Reals Lra ssrR Reals_ext realType_ext logb ssr_ext ssralg_ext bigop_ext fdist