Hi divoplade! I know there is reverse and I think I did implement it before, when working through SICP exercises. Thanks for that implementation and input though!
I think the point I wanted to make is rather to avoid `reverse` completely. If I had a vector, I could simply go by index backwards or forwards without adding any runtime complexity. But a vector is of defined length, not expandable like a list via cons, which means it might not be the best idea under some circumstances. Other circumstances make lists less ideal. If those circumstances appear together, then I probably should be using another data structure. Or pay the price in time complexity for some operations. I just read, that Python "lists" are actually implemented as https://en.wikipedia.org/wiki/Dynamic_array. So I guess a more specific but less generally useful question is: "What do I use in Guile, if I were using a dynamic array in Python?" I almost never find myself reversing a Python "list". Probably because it can be indexed in reverse order indices. Best regards, Zelphir On 11/22/20 8:45 PM, divoplade wrote: > Hello Zelphir! > > Le dimanche 22 novembre 2020 à 19:48 +0100, Zelphir Kaltstahl a écrit : >> However, when I use the list in >> reverse and ever need to output the lines in the list in their >> original >> order, I would first need to `reverse` the list again. > There is a "reverse" function; you could implement it yourself as a > tail-recursive function if you wanted (it's currently implemented in C, > so my guess is it's even more efficient). You don't need vectors for > that. > > (define (my-reverse-aux accumulation list) > (if (null? list) > accumulation > (my-reverse-aux (cons (car list) accumulation) (cdr list)))) > > (define (my-reverse list) > (my-reverse-aux '() list)) > > (my-reverse '(a b c d e f g h)) > -- repositories: https://notabug.org/ZelphirKaltstahl
