Re: [go-nuts] Generics - type inference - which type parameters?
Perhaps near the end of the type inference section, before "Note: type
inference is a convenience feature"? And perhaps something like this?
When discussing type inference, the term "type parameter" refers only to
the type parameters in a specific use of a generic function or type. For
example,
func Min[T interface{ type int, uint }](a, b T) T {
if b < a {
return b
}
return a
}
func Min3[U interface{ type int }](a, b, c U) U {
return Min(a, Min(b, c))
}
While inferring the type argument for the calls to Min, T is considered a
type parameter, but U is considered to be a fixed type, not subject to type
unification.
On Mon, Aug 24, 2020 at 4:47 PM Ian Lance Taylor wrote:
> On Mon, Aug 24, 2020 at 4:34 PM Patrick Smith
> wrote:
> >
> > I may be missing something, but it seems to me that one point in the
> draft's discussion of type inference could usefully be clarified (
> https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-type-parameters.md#type-inference
> ).
> >
> > The term "type parameter" there should be restricted to the type
> parameters in the specific use of a generic type or function for which we
> are trying to infer type arguments. For example (
> https://go2goplay.golang.org/p/pWis3rlJElu)
> >
> > func Min[type T interface{ type int, uint }](a, b T) T {
> >
> > if b < a {
> >
> > return b
> >
> > }
> > return a
> >
> > }
> >
> > func Min3[type U interface{ type int }](a, b, c U) U {
> >
> > return Min(a, Min(b, c))
> >
> > }
> >
> > func BadMin3[type V interface{ type int, uint, string }](a, b, c V) V {
> >
> > return Min(a, Min(b, c))
> >
> > }
> >
> > Here, U and V are type parameters, but when inferring type arguments for
> the calls to Min, we must consider U and V as fixed types, not subject to
> type unification. This seems needed in order for the compiler to reject
> BadMin3.
>
> Thanks. That seems fairly clear to me, but I'm probably too close to
> the problem. Any suggestions for exactly where we should add a
> sentence, and what that sentence should be? Thanks.
>
> Ian
>
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/CAADvV_ss02RaDP%2BT%2B7RMkzOOLN8vHjdgT7GO4q96TfJ%3DCKEOGw%40mail.gmail.com.
Re: [go-nuts] Generics - type inference - which type parameters?
On Mon, Aug 24, 2020 at 4:34 PM Patrick Smith wrote:
>
> I may be missing something, but it seems to me that one point in the draft's
> discussion of type inference could usefully be clarified
> (https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-type-parameters.md#type-inference).
>
> The term "type parameter" there should be restricted to the type parameters
> in the specific use of a generic type or function for which we are trying to
> infer type arguments. For example (https://go2goplay.golang.org/p/pWis3rlJElu)
>
> func Min[type T interface{ type int, uint }](a, b T) T {
>
> if b < a {
>
> return b
>
> }
> return a
>
> }
>
> func Min3[type U interface{ type int }](a, b, c U) U {
>
> return Min(a, Min(b, c))
>
> }
>
> func BadMin3[type V interface{ type int, uint, string }](a, b, c V) V {
>
> return Min(a, Min(b, c))
>
> }
>
> Here, U and V are type parameters, but when inferring type arguments for the
> calls to Min, we must consider U and V as fixed types, not subject to type
> unification. This seems needed in order for the compiler to reject BadMin3.
Thanks. That seems fairly clear to me, but I'm probably too close to
the problem. Any suggestions for exactly where we should add a
sentence, and what that sentence should be? Thanks.
Ian
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/CAOyqgcVOWb_snspcZ_mu8sBPSKV9jUHMp%2BGxVO1Q8E0PxQgcZQ%40mail.gmail.com.
[go-nuts] Generics - type inference - which type parameters?
I may be missing something, but it seems to me that one point in the
draft's discussion of type inference could usefully be clarified (
https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-type-parameters.md#type-inference
).
The term "type parameter" there should be restricted to the type parameters
in the specific use of a generic type or function for which we are trying
to infer type arguments. For example (
https://go2goplay.golang.org/p/pWis3rlJElu)
func Min[type T interface{ type int, uint }](a, b T) T {
if b < a {
return b
}
return a
}
func Min3[type U interface{ type int }](a, b, c U) U {
return Min(a, Min(b, c))
}
func BadMin3[type V interface{ type int, uint, string }](a, b, c V) V {
return Min(a, Min(b, c))
}
Here, U and V are type parameters, but when inferring type arguments for
the calls to Min, we must consider U and V as fixed types, not subject to
type unification. This seems needed in order for the compiler to reject
BadMin3.
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/CAADvV_uehufugSWsBfQZQQ55U58coPvv6XSTkuB%2B_ZEAdQcsDg%40mail.gmail.com.
