fact: Definition cast_fun_rV1 U (T : eqType) (X : U -> T) : 'rV[U]_1 -> T := fun x => X (x ``_ ord0).
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