On Thu, Sep 6, 2018 at 11:36 PM jimmy frasche <[email protected]>
wrote:
> To unify those cases you need something like haskell-style typeclasses
> where you can say this type satisfies this contract using these
> methods/operators.
>
FWIW, the Go way of doing that is embedding it in a new struct and
overwriting the methods - which is pretty much the only way to do it while
maintaining the property that only the owner of a type can define methods
on it.
So, you can already do this. But it requires you to write it. Which is
boilerplate.
(which I'm personally fine with, FTR :) )
>
>
> Even ignoring that, the contracts proposal doesn't let you write a
> generic variadic min/max since there's no way to get the
> smallest/largest value of a type so you can't write
>
> func min(type T ordered)(ts ...T) T {
> min := LargestPossible(T) // not possible
> for _, t := range {
> if t < min {
> min = t
> }
> }
> return min
> }
>
> You could get around that with the signature (firstOne T, rest ...T)
> but there's a larger point about the necessity of knowing numeric
> limits and properties for writing that kind of generic code in there.
>
>
> One way around the asymmetry between operators and methods that
> doesn't introduce any issues like operator methods or any of that is
> to have a package that defines types like
>
> package basic // not the best name
>
> type Int int
>
> type Slice(type T) []T
>
> // and so on for all the primitive and basic composite types
>
> and give all of those methods like Less and At. You'd have to do
> int(min(basic.Int(x), basic.Int(y))) but at least you wouldn't have to
> write the trivial wrapper methods. Not especially pretty.
>
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