On Wed, Jun 24, 2020 at 2:33 PM i3dmaster <[email protected]> wrote:
>
> example:
>
> type Key interface {
> type comparable, fmt.Stringer
> }
>
> type Value interface {
> type interface{}, copyable
> }
>
> type Container(type K Key, V Value) interface {
> Add(K, V) bool
> }
>
> type HashMap(type K Key, V Value) struct{ m map[K]V }
>
> func (h *HashMap(K,V)) Add(k K, v V) bool {
> h.m[k] =v
> return true
> }
>
> But of course, copyable isn't defined... So where to find some of these
> predefined constraints? Or if not, how could one define a such constraint?
>
> Also how to specify constrains like
>
> 1. A type that I can call len() against it?
> 2. A type that I can range over it?
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The current generics design draft doesn't support the kind of
constraints you are looking for.
I'm not even sure what you mean by "copyable". All Go types can be copied.
Typically instead of writing generic type constraints like supports
len or range people write code that takes a slice of some generic
type.
Note that you are using type lists in a way that doesn't look right.
To write a constraint that is a combination of other constraints, you
should use embedding, as in
type Key interface {
comparable
fmt.Stringer
}
Ian
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