Oh and FWIW: You are right (in my opinion) that the different things `clear` does are, well, different. But note that clear is not the only builtin for which that is the case. `make`, `len` and `cap` all do different things (to varying degrees) on maps, slices and channels. That's not necessarily a good reason to add more builtins that do different things, but there is precedent.
On Thu, Jul 6, 2023 at 8:14 AM Axel Wagner <axel.wagner...@googlemail.com> wrote: > On Thu, Jul 6, 2023 at 7:49 AM Henry <henry.adisuma...@gmail.com> wrote: > >> So, if I get this right, clear on map will result in map length equals to >> zero, but clear on slice is only a value-zeroing operation and the slice >> length remains unchanged? > > > That understanding is correct. > > >> They seem like two different operations to me. I don't think that >> built-in clear function is necessary. It doesn't seem like the function has >> a good reason to be there. >> > > There is one thing that `clear` allows which is impossible without it and > that's removing irreflexive keys (those that contain floating point > types/elements/fields which are NaN) from a map. > > Whether that's a "good" reason is up for debate, of course. There has been > quite a bit of that in the issue already: > https://github.com/golang/go/issues/56351 > > >> >> On Wednesday, July 5, 2023 at 3:54:43 PM UTC+7 Tharaneedharan Vilwanathan >> wrote: >> >>> Hi Axel, >>> >>> Okay, that helps! Thanks for the details. >>> >>> Regards >>> dharani >>> >>> >>> On Wed, Jul 5, 2023 at 1:38 AM Axel Wagner <axel.wa...@googlemail.com> >>> wrote: >>> >>>> Hi, >>>> >>>> this has come up on the issue as well. Robert Griesemer provided an >>>> explanation >>>> <https://github.com/golang/go/issues/56351#issuecomment-1601751291>: >>>> >>>> If the argument type (the type of the argument provided to clear) is a >>>>> type parameter (is of type parameter type), all types in its type set (in >>>>> the type set of the constraint corresponding to the type parameter) must >>>>> be >>>>> maps or slices, and clear performs the operation corresponding to the >>>>> actual type argument (corresponding to the type of the actual type >>>>> argument >>>>> with which the type parameter was instantiated). >>>> >>>> >>>> That is, the sentence is about this situation: >>>> >>>> func Clear[T, any, S ~[]T](s S) { >>>> clear(s) >>>> } >>>> func main() { >>>> Clear(make([]int, 42)) >>>> } >>>> >>>> In this case, the type of s is S, which is a type parameter. So `clear` >>>> performs the operation corresponding to the type argument - in this example >>>> []int. >>>> >>>> The sentence is a bit confusing (I've seen this question come up four >>>> times now), so it probably should be clarified a bit. >>>> >>>> On Wed, Jul 5, 2023 at 9:06 AM Tharaneedharan Vilwanathan < >>>> vdha...@gmail.com> wrote: >>>> >>>>> Hi All, >>>>> >>>>> Go 1.21 introduces a new clear() builtin function. I see this text in >>>>> https://tip.golang.org/ref/spec#Clear: >>>>> >>>>> clear(t) type parameter see below >>>>> >>>>> If the argument type is a type parameter >>>>> <https://tip.golang.org/ref/spec#Type_parameter_declarations>, all >>>>> types in its type set must be maps or slices, and clear performs the >>>>> operation corresponding to the actual type argument. >>>>> >>>>> I am not able to make sense of it. What does this mean? Any examples >>>>> on the usage? >>>>> >>>>> Appreciate your help. >>>>> >>>>> Thanks >>>>> dharani >>>>> >>>>> -- >>>>> 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...@googlegroups.com. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/d/msgid/golang-nuts/CAN-HoCn99D-m71aJr3DRzCJvk_c7h8OhG2O4wPC-1Wd2ruEYNg%40mail.gmail.com >>>>> <https://groups.google.com/d/msgid/golang-nuts/CAN-HoCn99D-m71aJr3DRzCJvk_c7h8OhG2O4wPC-1Wd2ruEYNg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> >>>> -- >> 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/00e424f1-1a62-4183-8974-9a585960ce7dn%40googlegroups.com >> <https://groups.google.com/d/msgid/golang-nuts/00e424f1-1a62-4183-8974-9a585960ce7dn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- 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/CAEkBMfEsZ67fQEqOPMNEj%3Dgz5Y%2Bz5kgjPSHR8casGvt8YzaFuw%40mail.gmail.com.
