I look at what Carla did write and it feels ... good. I don't know, it may
be not for everyone, but for me [T any] looks cleaner than [type T].
Probably I see `[` and understand this is generic params, then `T` and I
immediately understand this is how the generic type denoted. A final touch,
I would seriously consider this idea.
суббота, 25 июля 2020 г. в 23:22:24 UTC+3, Ian Lance Taylor:
> On Sat, Jul 25, 2020 at 11:47 AM 'Carla Pfaff' via golang-nuts
> <golan...@googlegroups.com> wrote:
> >
> > To expand on my post:
> > It would be very consistent with the structure of regular parameter
> lists. Just like every parameter in a regular parameter list must have a
> type (with the exception of multiple consecutive parameters having the same
> type), every type parameter in a type parameter list must have a constraint.
>
> That is certainly true.
>
> But it is also true, based on experiments writing generic code, that
> the majority of type parameters have no constraints. That is
> particularly true for type parameters of generic types. So while it
> would be possible to require people to always explicitly write a
> constraint, it seems painful to force people to always write something
> that is almost never needed.
>
> Note that in this way constraints on type parameters are different
> from types of regular parameters. It makes no sense to speak of a
> regular parameter with no type. It's entirely reasonable, even
> common, to speak of a type parameter with no constraint.
>
> Ian
>
>
> > On Saturday, 25 July 2020 at 20:26:37 UTC+2 Carla Pfaff wrote:
> >>
> >> I just discovered the experiment to make the "type" keyword optional in
> certain cases on the dev.go2go branch. The commit message says:
> >>
> >> ---
> >> Experiment: Make "type" keyword optional in generic type declarations
> when
> >> it is clear that we can't have an array type declaration. This is the
> case
> >> when we have one the following:
> >>
> >> - more than one type parameter
> >> - a type parameter with a constraint
> >> - a trailing comma in the type parameter list
> >> --
> >>
> >> If the "type" keyword is not necessary if a constraint is present, then
> why not make a constraint mandatory and get rid of the "type" keyword in
> type parameter lists altogether?
> >>
> >> Before:
> >>
> >> func Filter[type Elem](...)
> >> func Map[Elem1, Elem2](...)
> >> func Max[Elem constraints.Ordered](...)
> >>
> >> After:
> >>
> >> func Filter[Elem interface{}](...)
> >> func Map[Elem1, Elem2 interface{}](...)
> >> func Max[Elem constraints.Ordered](...)
> >>
> >> "interface{}" may be a little bulky, especially it since it is usually
> used for the simple cases. But if there was a short type alias for
> "interface{}" like "any" it can look good:
> >>
> >> type any = interface{}
> >>
> >> func Filter[Elem any](...)
> >> func Map[Elem1, Elem2 any](...)
> >> func Max[Elem constraints.Ordered](...)
> >>
> > --
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> .
>
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