proposition: Lemma dunit1E x y : (dunit x) y = (x == y)%:R.
proof: Proof. by unlock dunit; rewrite drat1E /= !(simpm, invr1). Qed.
imports: mathcomp(all_ssreflect all_algebra) mathcomp.classical(boolp classical_sets mathcomp_extra) xfinmap ereal reals discrete topology realseq realsum