How to detect if any rows were returned in plpgsql function?

Hello.

If I write two functions (with appologies for any syntax error)

create function bar() returns set of integer language plpgsql as $$
begin
return query select something.....;
end; $$;

create function foo() returns set of integer language plpgsql as $$
begin
return query select * from bar();
end; $$;

how can I before the function foo ends, check if I got any data back
from the call to bar() ?