On Thursday, June 18, 2020 at 5:53:28 AM UTC-4, Axel Wagner wrote:
>
>
>
> On Thu, Jun 18, 2020, 11:28 T L <tapi...@gmail.com <javascript:>> wrote:
>
>> How to declare a generic functions which converting a slice with type Ta
>> to a slice with type Tb. Like
>> func ConvertSlice(type Ta, Tb constraint)(ins []Ta) []Tb {...}
>>
>>
>>
For example, I need a ConvertSlice function which will do
* Convert []int to []int64, and the inverse
* Convert string to []byte, and the inverse
* Convert between several struct types with the same field set, except
their field tags are different.
* more generally, Convert []Ta to []Tb, and the inverse, where Ta can be
converted to Tb.
> How to constraint a type parameter must be of an interface type?
>>
>
> I don't think you can. Why would you need to? Note that there will always
> be constraints that you can't express.
>
One need is the same as the above Convert case, there should be more.
func ConvertSlice(type T, I constraint)(ins []T) []I {...}
Where I must/may be some special interface types.
>
>> Is it possible to define generic unnamed types?
>>
>
> No. It also would be useless. You can't refer to a generic, uninstantiated
> type. So a generic type either needs a name to be referred by to
> instantiate it, or be instantiated right immediately in its declaration
> (and thus wouldn't need to be generic).
>
> If it is impossible, then how to define a generic map type which elements
>> must be an unnamed integer slice?
>>
>
> type numeric interface {
> type int, int8, int16, int32, ...
> }
>
> type MyMap(type K comparable, T numeric) map[K][]T
>
Sorry, here I meant "... must be of a slice with an unnamed element type".
Sometimes, the map element slice type itself might be required to be shown
as a type parameter.
One of the case is still related to slice conversions.
>
> --
>> 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 golan...@googlegroups.com <javascript:>.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/golang-nuts/f02971c4-7e16-4f33-b919-93e7569d6571o%40googlegroups.com
>>
>> <https://groups.google.com/d/msgid/golang-nuts/f02971c4-7e16-4f33-b919-93e7569d6571o%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/0ef1456d-8d8c-4d74-a36a-82e2b3337765o%40googlegroups.com.
