> sorts defined by an ordering function purely dependent on the value of the element
Hmm, I thought the function was agnostic to what really get compared? If it offers two index numbers, and the return value says the one with larger index number should be at the front, shouldn't the sort function simply do that, since during the sorting, the passed index number should be stable? On Wednesday, December 7, 2022 at 11:14:37 AM UTC+8 harr...@spu.edu wrote: > Oh, to reverse by index ... I think this doesn't quite fit in the idea of > sorts defined by an ordering function purely dependent on the value of the > element. > > I think there may have been a feature request > <https://github.com/golang/go/issues/47988> for a `slices.Reverse` > function in golang.org/x/exp/slices - I'm not sure what the status or > reasoning is on this. FWIW it's not the only approach that might make sense > for traversing a slice in reverse order, and it can be naive when working > with e.g. bytes holding utf8. > > I think this works but I haven't really thought about edge cases... > > `reverse(&s)` > > func reverse[T any](s *[]T) { > z := len(*s) > for a := 0; a < len(*s)/2; a++ { > (*s)[a], (*s)[z-a-1] = (*s)[z-a-1], (*s)[a] > } > } > > On Tuesday, December 6, 2022 at 6:54:38 PM UTC-8 hey...@gmail.com wrote: > >> Thanks for the quick reply. >> >> But that seems to compare values. I'd like to compare index numbers. The >> fact that original values follow index number order is a coincidence. >> >> > I think it'd be recommended to look at the generics slices package, >> which also has a sort >> >> Do you mean golang.org/x/exp/slices? That also seems to only compare >> values. >> >> >> On Wednesday, December 7, 2022 at 10:45:33 AM UTC+8 harr...@spu.edu >> wrote: >> >>> Subtly: >>> return s[i] > s[j] >>> >>> Is the right sort func >>> >>> I think it'd be recommended to look at the generics slices package, >>> which also has a sort >>> On Tuesday, December 6, 2022 at 6:39:29 PM UTC-8 hey...@gmail.com wrote: >>> >>>> Hi, >>>> >>>> I have this very simple sorting code: >>>> >>>> s := make([]int, 0, 100) >>>> for i := 1; i <= 20; i++ { >>>> s = append(s, i) >>>> } >>>> sort.Slice(s, func(i, j int) bool { return i > j }) >>>> log.Print(s) >>>> >>>> I expect it to print numbers in reverse order, since items with larger >>>> index numbers should be at the front. However, at lease in go1.19.3, it >>>> prints >>>> >>>> [9 1 8 5 16 3 20 2 10 7 12 13 14 15 6 4 19 18 17 11] >>>> >>>> I guess I must have misunderstood how the sort package works, but >>>> rereading sort's doc multiple time doesn't help answer the question. >>>> >>>> Could anyone shed some light? >>>> >>> -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/5fb85879-b356-4d6d-9645-778d3e7c549an%40googlegroups.com.
