There is only one top-level namespace 'std', but there is at least one
nested namespaces, namely 'std::rel_ops'.
And I think that's the only one.
I don't find it remarkable that there's only one top-level namespace
'std', but I think the single nested namespace 'std::rel_ops' /is/
remarkable. Why is it there? And the answer is simple: because many
programmers tend to write 'using namespace std;', but would not like to
then have the standard library's operators imposed on them, i.e. that in
this special case the namespaces is /needed/.
Of course: it is a relevant consideration.
Cheers, & hth.,