proposition: Lemma expeR_total x : 0 <= x -> exists y, expeR y = x.
proof: Proof. move: x => [r|_|//]; last by exists +oo. rewrite le_eqVlt => /predU1P[<-|]; first by exists -oo. by rewrite lte_fin => /expR_total[y <-]; exists y%:E. Qed.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum matrix) mathcomp(interval rat) mathcomp(boolp classical_sets functions) mathcomp(mathcomp_extra) reals ereal signed topology normedtype landau sequences derive realfun itv convex