Benchmark: timing 10000 iterations of For_C, For_Set...
     For_C: 14 wallclock secs (14.33 CPU) @ 697.84/s (n=10000)
   For_Set:  7 wallclock secs (7.22 CPU) @ 1385.04/s (n=10000)
          Rate   For_C For_Set
For_C    698/s      --    -50%
For_Set 1385/s     98%      --