Benchmark: timing 10000 iterations of flatten, straight...
   flatten:  6 wallclock secs ( 5.08 usr +  0.00 sys =  5.08 CPU) @ 1969.28/s (n
=10000)
  straight:  0 wallclock secs ( 0.00 usr +  0.00 sys =  0.00 CPU)
            (warning: too few iterations for a reliable count)