Just as an intuitive argument, we could do:
sort.Slice(s, func(i, j int) bool { log.Println(i, j); return i > j })The appearances of i and j per step recapitulate the logic of the sorting algo in some weak sense; not slice order On Tuesday, December 6, 2022 at 7:28:39 PM UTC-8 hey...@gmail.com wrote: > > 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/0210cff1-ddc2-44a6-a3d3-73b199011561n%40googlegroups.com.
