> I investigated tuples a bit, it's close. The one thing I'd need is
> being able to index the values using a variable. The tuple.i
> notation apparently doesn't work (or I did not try hard
> enough). Also, for low-level things that will be mapped to GPU
> memory, precise/predictable/settable alignment is needed.This might be a bit hacky but I just wanted to point out there exists
a way to index into tuples. You can use the Mirror(reflecting:
tuple).children syntax. You can loop over the values of the tuple and
even though a bit awkward you can even use indices to index into the
children.
True, but the inefficiency of that approach pretty much defeats the
purpose of having a fixed-sized array.
···
on Thu Aug 04 2016, Manav Gabhawala <swift-evolution@swift.org> wrote:
Regards,
Manav GabhawalaOn August 4, 2016 at 5:18:13 AM, James Froggatt via swift-evolution > (swift-evolution@swift.org(mailto:swift-evolution@swift.org)) wrote:
On 4 Aug 2016, at 13:00, Raphael Sebbe wrote:
> Thank you Chris, James.
>
> I'm answering James feedback/questions below.
>
> On Thu, Aug 4, 2016 at 1:57 AM James Froggatt wrote:
>
> > What are your thoughts on using tuples for this?
> >
> > typealias CGPoint4 = (CGPoint, CGPoint, CGPoint, CGPoint)
> >
> > struct Quad { var corners: CGPoint4 }
> >
> > var fixedLength = (point1, point2, point3, point4)
> > print(fixedLength.0)
> > print(fixedLength.4) //compiler error, not an element of the tuple
> >
> >
> > With shorthand declaration syntax, this would have the benefits
> > of a fixed-length array with added compile-time safety. A
> > previously suggested syntax was along the lines of '(CGPoint *
> > 4)'.
> >
>
> I investigated tuples a bit, it's close. The one thing I'd need is
> being able to index the values using a variable. The tuple.i
> notation apparently doesn't work (or I did not try hard
> enough). Also, for low-level things that will be mapped to GPU
> memory, precise/predictable/settable alignment is needed.Good point. A similar mechanism might be possible eventually for
tuples, but right now this isn't possible.
> > > 4. Reference/pointer to structs: accessing & modifying structs
> > > deep into the model currently requires fully qualified path to
> > > the struct instance. Fully qualifying an inner struct in your
> > > data model can be very tedious, depending on model complexity.
> > >
> > > For instance, with scoped access solutions made with Swift 3,
> > > you need to cascade blocks if you need to access multiple
> > > inner structs, which doesn't scale well as it creates code
> > > pyramids:
> > >
> > > scopedAccess(&varA) {
> > > scopedAccess(&varB) {
> > > // modify varA & varB
> > > }
> > > }
> > >
> > > It's easily done in C/C++ using pointers/references. To make
> > > that better, we'd need some kind of language support IMO.
> > >
> > >
> >
> >
> > Could this be generalised, maybe with a reference-semantic ‘property accessor’?
> >
> > Example:
> >
> > let get: () -> Bool = #get(controller.view.isVisible)
> > print(get())
> >
> > let set: (Bool) -> () = set(controller.view.isVisible)
> > set(true)
> >
> > let accessor: Lens = #lens(controller.view.isVisible)
> > print(accessor.value)
> > accessor.value = true
> >
> > This would have the added bonus of also tracking the
> > reassignment of reference-type properties - in this example, if
> > 'view' is reassigned, the referenced value is updated.
>
> Sounds good, I'm not aware of this syntax. Will investigate, thanks.Sorry, I was suggesting a *possible* syntax. No such syntax
currently exists, though the functionality can be imitated with
closures:let get: () -> Bool = {controller.view.isVisible}
print(get())let set: (Bool) -> () = {controller.view.isVisible = $0}
set(true)struct Lens {
var get: () -> T
var set: (T) -> ()
var value: T { get { return get() } set { set(newValue) } }
}
let accessor: Lens = Lens(get: {controller.view.isVisible}, set:
{controller.view.visible = $0})
print(accessor.value)
accessor.value = trueIt's a bit more verbose when creating the get-set accessor, and may
not perform optimally, but it's actually pretty functional.
>
> >
> > > 5. Memory / pointer access, including casting. It's too
> > > verbose currently IMO when compared to C. Should be better
> > > supported for a language that is also targeting low-level
> > > (network, disk storage). A syntax that is both fast (like C)
> > > and safe would be great.
> >
> > Not familiar with low-level programming in Swift, but have you
> > considered creating domain-specific operators?
> > For example, I imagine something like 'UnsafeMutablePointer(v)'
> > could be reduced to '*v'.
> >
> >
>
> Do you mean operator is available only within a limited scope?
> That would be interesting, because I don't want to pollute global
> scope with such all-purpose operator. Sounds that I need to
> investigate that as well.If you have a specific module which performs this sort of operation
a lot, you can just declare the operator as internal. If it's needed
in several, making a separate module for the operators could be
preferable.
> >
> > > 7. I'm also fan of async/await kind of stuff, asynchronous
> > > flows, etc., but this has already been mentioned -> cool!
> >
> > I would like to see some ideas in this area.
> > async/await never really clicked for me until I realised it's
> > just syntactic sugar - 'await' actually ends the function, and
> > everything below is an implicit callback. Personally I feel like
> > Swift's trailing closure syntax makes callbacks lightweight
> > enough that this isn't so much of an issue. Something focusing
> > more on the memory-management and thread-safety aspects of
> > asynchronous code does seem useful in the context of Swift.
> >
> >
> > >
> Sure thread-safety, atomicity features would be really nice & useful.
>
> The one problem I have with closure syntax (trailing or not, I
> like trailing too), is that when you chain a few of them, which is
> pretty frequent is async programming, you end up with a closure
> pyramid. It doesn't scale well beyond 2 or 3 levels.Makes sense. _______________________________________________
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--
-Dave