On Sunday, 30 September 2018 13:04:55 UTC+2, Robert Engels wrote:
>
> The static switch is a big problem. For any complex method you are going
> to completely duplicate all of the code. Not good.
>
> Far better to map operators to interfaces then you only need a single
> method implementation.
>
I don't think you can easily do that with Go, take for example the
constraint (according to the draft proposal syntax and semantics)
contract unsigned(x T) {
1 << x
}
Another problem is pointer dereferencing
contract p(x T) {
*x
}
if you define an operator for pointer dereferencing on T by a method, then
all the rules about what is addressable and dereferencable in Go become
very complicated, especially w.r.t. interfaces
Finally, all standard languages with operator overloading either
1) don't allow you to implement numbers generically for implementations
where constants for 0, 1, Pi, ... may have different binary representation
than the constant in the language (such as fixed point numbers); or
2) like C++ allow constants to be substituted via templates.
I think some of the literature on "Dependent types" may address this later
issue, but it's pretty heady stuff and outside the scope of
what I want to have to think about when coding, so as to focus efforts more
readily on the objective of the code rather than heady type theory.
practical operator overloading isn't a solved problem AFAIK, much less for
Go.
Scott
>
> On Sep 30, 2018, at 5:33 AM, Christian Surlykke <chri...@surlykke.dk
> <javascript:>> wrote:
>
> Hi
>
> I made a proposal for generics with constraints about ½ a year ago, which
> I posted to the (very long) thread on issue 15292. I've now made a version
> 2 <https://github.com/surlykke/Go-Generics-with-constraints/tree/V2.0>,
> in case anybody would like to read it.
>
> This version adapts to the generics syntax now proposed by the Go team and
> is somewhat simpler than the previous version.
>
> br. Chr.
>
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