Benchmark: timing 500000 iterations of foo_or, foo_qs, foo_ro...
    foo_or:  3 wallclock secs ( 2.55 usr +  0.00 sys =  2.55 CPU) @ 196386.49/s (n=500000)
    foo_qs:  3 wallclock secs ( 2.45 usr +  0.00 sys =  2.45 CPU) @ 203832.04/s (n=500000)
    foo_ro:  2 wallclock secs ( 2.39 usr +  0.00 sys =  2.39 CPU) @ 209205.02/s (n=500000)
           Rate foo_or foo_qs foo_ro
foo_or 196386/s     --    -4%    -6%
foo_qs 203832/s     4%     --    -3%
foo_ro 209205/s     7%     3%     --