On Mon, Jun 22, 2020 at 4:04 PM Robert Engels <reng...@ix.netcom.com> wrote:
>
> The list of types supporting LessThan is not finite, is unbounded. The list
> of types supporting < is finite. But < could of been viewed as syntactic
> sugar if the Go designers so chose.
Actually, the list of types supporting LessThen contains only one
type: interface {LessThan() bool}
I didn't see in the draft design a limitation on the types that can be
listed in a type list. So can a type list contain an interface?
If that is the case, I will repeat my suggestion to take type lists
outside interfaces and make them their own construct. Maybe call it
something else, like typeconstraint:
typecontstraint T int, string, OtherType
>
> > On Jun 22, 2020, at 4:01 PM, burak serdar <bser...@computer.org> wrote:
> >
> > On Mon, Jun 22, 2020 at 2:53 PM Ian Lance Taylor <i...@golang.org> wrote:
> >>
> >>> On Mon, Jun 22, 2020 at 1:41 PM Ankur Agarwal <akah...@gmail.com> wrote:
> >>>
> >>> I like the idea of generics, and having played around with them it
> >>> definitely feels worth bringing into Golang. But, I agree with the author
> >>> of this post and I don't think constraints on generics is needed.
> >>>
> >>> I do understand the arguments that:
> >>> 1. There's no implicit conversion between a value type and an interface,
> >>> and constraints would make this possible, but i feel that it's at the
> >>> expense of making the language unnecessarily complicated. Can we not just
> >>> think through our design of our applications to either prevent this need
> >>> or ensure that we build a slice of interfaces?
> >>> 2. Being able to constrain on comparable values (using <,>,==,!=).
> >>> Couldn't we create an interface which declares what we need (LessThan,
> >>> MoreThan, etc)? I feel that if the language goes down this path, why not
> >>> do the whole shebang and have operator overloading in go?
> >
> > It does not make much sense to constrain a type to have less-then,
> > greater-than support in a language without operator overloading. There
> > is a finite list of types that support LessThan, so it is more
> > explicit and simpler to list the types you expect in a generic
> > function (think "i expect to receive a string or int" as opposed to "i
> > expect to receive a type that supports <". The second one will let you
> > pass a float64, which may be unexpected.) And I believe many Go users
> > are happier because there is no operator overloading.
> >
> >
> >>>
> >>> I've yet to really feel the need for either of these (although i'm not a
> >>> veteran golang dev -- only 1 year with golang in a professional
> >>> environment), but I have come across scenarios where generics would
> >>> otherwise be useful... (and function overloading, but that's a whole
> >>> different kettle of fish)
> >>>
> >>> It's great that we've been given the chance to give some feedback :)
> >>
> >> I'm sorry, I'm not sure quite what you are saying. The reason for
> >> constraints is to create a contract between the generic function and
> >> its caller, so that far away code doesn't break unexpectedly. See
> >> https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-type-parameters.md#constraints
> >> .
> >>
> >> Are you talking about type lists, rather than constraints?
> >>
> >> Ian
> >>
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