proposition: Lemma drat1E s x : drat s x = (count_mem x s)%:R / (size s)%:R.
proof: Proof. by unlock drat; rewrite mkdistrE. Qed.
imports: mathcomp(all_ssreflect all_algebra) mathcomp.classical(boolp classical_sets mathcomp_extra) xfinmap ereal reals discrete topology realseq realsum