Constant here is just an example. We can use varaibles.
var a, b int
c := max(a,b)
on the base of type inference.
Predeclared types don't have methods.But we can extend the type
restriction, using implicit type conversion here, between BiggerInt and
int, BiggerFloat and float32.
I think the implicit type conversion here is better than type list in
interface.
On Tuesday, December 29, 2020 at 1:35:37 AM UTC+8 Ian Lance Taylor wrote:
> On Mon, Dec 28, 2020 at 3:30 AM redsto...@gmail.com
> <redsto...@gmail.com> wrote:
> >
> > If generic is inevitable, make it better. The type list in the current
> draft is so special that it is added only for operators. I think it will
> bring complexity and inconsistens in go. So I get an idea to replace it.
> >
> > type bigger[T bigger] interface{
> > BiggerThan(T) bool
> > }
> >
> > func max[T bigger[T]](a, b T) T{
> > if a.BiggerThan(b) {
> > return a
> > } else {
> > return b
> > }
> > }
> >
> > type BiggerInt int
> >
> > func (a BiggerInt) BiggerThan(b BiggerInt)bool{
> > return a > b
> > }
> >
> > type BiggerFloat float32
> >
> > func (a BiggerFloat) BiggerThan(b BiggerFloat)bool{
> > return a > b
> > }
> >
> >
> > max(1,2)
> >
> > instead of operators we use method. the generic call site remain the
> same.
> > If we allow the implicity type conversion between BiggerInt and int,
> this will work.
> >
> > This solution will write more code when we define BiggerThan in each
> type. But we remove type list in interface. How do you think it?
>
> I think that one of the minimal requirements for any generics proposal
> is the ability to write a Max function that works for variables (not
> constants) of any integer or floating-point type. If we can't write
> Max, then there are all sorts of useful functions that we can't write.
> And since the predeclared types don't have methods, the approach you
> describe doesn't permit us to write Max.
>
> Ian
>
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