On Sun, Mar 16, 2014 at 2:55 PM, Patrick Useldinger <uselpa.l...@gmail.com> wrote: > > > My questions are: > > (1) Is Racket "tail-recursive modulo cons"? If not, is there a reason for > this?
Racket is not "tail-recursive modulo cons". > (2) Is the last example "reverse free" or does it use reverse under the > hood? `for/list` uses `reverse` internally -- you can see for yourself how this works by using the Macro Stepper. > (3) finally, what is the recommended way to write this procedure in terms of > performance? I took your program, and made all the functions run on much longer lists. Here are the timings: $ r /tmp/even-list.rkt 'plain cpu time: 1288 real time: 1294 gc time: 936 't cpu time: 440 real time: 441 gc time: 320 'for/fold cpu time: 484 real time: 485 gc time: 328 'mcons cpu time: 204 real time: 204 gc time: 148 'mcons-convert cpu time: 632 real time: 631 gc time: 416 'for/list cpu time: 460 real time: 460 gc time: 332 'mcons-convert is one that uses `mcons`, but converts back to plain `cons` at the end. Sam ____________________ Racket Users list: http://lists.racket-lang.org/users
