fact: Definition sigma_finite d (T : semiRingOfSetsType d) (R : numDomainType) (A : set T) (mu : set T -> \bar R) := exists2 F : (set T)^nat, A = \bigcup_(i : nat) F i & forall i, measurable (F i) /\ mu (F i) < +oo.
imports: mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality fsbigop ) reals ereal signed topology normedtype sequences esum numfun HB(structures)