Re: [go-nuts] Re: Is there a way to eliminate the code repetition in the code?
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
> 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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Re: [go-nuts] Re: Is there a way to eliminate the code repetition in the code?
On Tue, Mar 22, 2022 at 6:01 AM 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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[go-nuts] Re: Is there a way to eliminate the code repetition in the code?
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
}
>
>
> On Sunday, March 20, 2022 at 11:36:27 PM UTC+7 tapi...@gmail.com wrote:
>
>>
>>
>> package main
>>
>> type A interface {
>> Ma()
>> }
>>
>> type B interface {
>> Mb()
>> }
>>
>> type Ta struct { A }
>>
>> type Tb struct { B }
>>
>> func ConvertSliceToA[From A](vs []From) []A {
>> var r = make([]A, len(vs))
>> for i := range vs {
>> r[i] = vs[i]
>> }
>> return r
>> }
>>
>> func ConvertSliceToB[From B](vs []From) []B {
>> var r = make([]B, len(vs))
>> for i := range vs {
>> r[i] = vs[i]
>> }
>> return r
>> }
>>
>> func main() {
>> var x [100]Ta
>> var _ = ConvertSliceToA(x[:])
>>
>> var y [100]Tb
>> var _ = ConvertSliceToB(y[:])
>> }
>>
>
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[go-nuts] Re: Is there a way to eliminate the code repetition in the code?
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
On Sunday, March 20, 2022 at 11:36:27 PM UTC+7 tapi...@gmail.com wrote:
>
>
> package main
>
> type A interface {
> Ma()
> }
>
> type B interface {
> Mb()
> }
>
> type Ta struct { A }
>
> type Tb struct { B }
>
> func ConvertSliceToA[From A](vs []From) []A {
> var r = make([]A, len(vs))
> for i := range vs {
> r[i] = vs[i]
> }
> return r
> }
>
> func ConvertSliceToB[From B](vs []From) []B {
> var r = make([]B, len(vs))
> for i := range vs {
> r[i] = vs[i]
> }
> return r
> }
>
> func main() {
> var x [100]Ta
> var _ = ConvertSliceToA(x[:])
>
> var y [100]Tb
> var _ = ConvertSliceToB(y[:])
> }
>
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