Is it hard to add two predeclared constraints, convertibleFrom and
convertibleTo, just like comparable?
On Tuesday, March 22, 2022 at 11:07:41 PM UTC+8 Ian Lance Taylor wrote:
> On Tue, Mar 22, 2022 at 6:01 AM tapi...@gmail.com <tapi...@gmail.com>
> wrote:
> >
> >
> >
> > On Monday, March 21, 2022 at 3:29:44 PM UTC+8 Henry wrote:
> >>
> >> Perhaps something like this?
> >> ```go
> >> func Convert[T, A any](src []T, converter func(T) A) []A {
> >> result := make([]A, len(src))
> >> for index, a := range src {
> >> result[index] = converter(a)
> >> }
> >> return result
> >> }
> >> ```
> >> See https://play.golang.com/p/rq89Wposc-D
> >
> >
> > It might reduce some code (surely not eliminate), but it is very
> ungraceful.
> >
> > The current constraint design lacks of two abilities:
> > 1. The ability of specifying a type argument must be an interface type.
> > 2. The ability of specifying a type argument must not be an interface
> type.
> >
> > I except an implementation like
> >
> > func ConvertSlice[From implements(To), To interface](vs []From) []To {
> > var r = make([]To, len(vs))
> > for i := range vs {
> > r[i] = vs[i]
> > }
> > return r
> > }
>
> I think it would be simpler to look for a way to express that one type
> parameter is convertible to another type parameter, as I suggested
> earlier. I don't see a need to distinguish between interface and
> non-interface types, or to introduce the notion of whether one type
> parameter implements another.
>
> Ian
>
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