Benchmark: timing 10 iterations of direct, iterate, recurse...
    direct:  0 wallclock secs ( 0.24 usr +  0.01 sys =  0.25 CPU) @ 40.00/s (n=10)
            (warning: too few iterations for a reliable count)
   iterate:  8 wallclock secs ( 7.81 usr +  0.00 sys =  7.81 CPU) @  1.28/s (n=10)
   recurse:  8 wallclock secs ( 7.73 usr +  0.00 sys =  7.73 CPU) @  1.29/s (n=10)
          Rate iterate recurse  direct
iterate 1.28/s      --     -1%    -97%
recurse 1.29/s      1%      --    -97%
direct  40.0/s   3024%   2992%      --