public static decimal Sum <TPredicate>(this ReadOnlyMemoryWhereRefEnumerable <decimal?, TPredicate> source)
where TPredicate : struct, IFunctionIn <decimal?, bool>
=> source.source.Span.SumRef <decimal?, decimal, TPredicate>(source.predicate);
public static int Sum <TPredicate>(this ReadOnlyMemoryWhereRefEnumerable <int?, TPredicate> source)
where TPredicate : struct, IFunctionIn <int?, bool>
=> source.source.Span.SumRef <int?, int, TPredicate>(source.predicate);
public static long Sum <TPredicate>(this ReadOnlyMemoryWhereRefEnumerable <long?, TPredicate> source)
where TPredicate : struct, IFunctionIn <long?, bool>
=> source.source.Span.SumRef <long?, long, TPredicate>(source.predicate);
