Benchmark: timing 10000 iterations of iterate, recurse...
   iterate:  2 wallclock secs ( 1.53 usr +  0.00 sys =  1.53 CPU) @ 6535.95/s (n=10000)
   recurse: 23 wallclock secs (22.82 usr +  0.00 sys = 22.82 CPU) @ 438.21/s (n=10000)
          Rate recurse iterate
recurse  438/s      --    -93%
iterate 6536/s   1392%      --