[swift-evolution] [Review] SE-0029 Remove implicit tuple splat behavior from function applications

[Jens Persson]

-0.5, I agree with Andrew Bennett and Brent Roayal-Gordon.

I use this functionality a lot, which means I've had to experience and
navigate around the inconsistencies and bugs of the current implementation,
but removing this functionality all together would leave us with a
significantly less capable/expressive language.

IMHO this (albeit buggy) aspect of the language is what allows one of its
key must-have-features, namely being able to work with generic higher order
functions in an (almost) acceptable way.

Suddenly loosing the ability to write and use higher order generic
functions (eg generic function composition, generic function application,
without having to special-case for every arity etc) would severely bloat my
code and decrease my productivity.

I was delighted to see Swift resurfacing these simple yet powerful and,
really, basic tools of programming. Now I'm not sure what to expect. I fear
that I will have to seriously consider moving back to using C++ templates :
( or perhaps resort to always use only a single tuple parameter, like eg
this:
func f(args: (T, T)) -> T { ... }
instead of this:
func f(a: T, b: T) -> T { ... }
How else would I be able to do simple stuff like composing them etc?

/Jens


On Tue, Feb 9, 2016 at 10:13 AM, Jerome ALVES via swift-evolution <
swift-evolution at swift.org> wrote:

> Hello,
>
> I use this feature to make generic "weak target actions" like this :
>
>
> func weakTarget<T, S: AnyObject>(target: S, action: S -> (T -> Void)) ->
> (T -> Void) {
>     return { [weak target] (input: T) -> Void in
>         guard let target = target else { return }
>         return action(target)(input)
>     }
> }
>
> class Target {
>     init() {}
>     func printHello(firstName: String, lastName: String) {
>         print("Hello \(firstName) \(lastName) !")
>     }
> }
>
> class Receiver {
>     init() {}
>     var printSomething: ((String, String) -> Void)? = nil
> }
>
> var aTarget: Target? = Target()
> let aReceiver = Receiver()
>
> aReceiver.printSomething = weakTarget(aTarget!, action: Target.sayHello)
>
> aReceiver.printSomething?("Jérôme", "Alves") // => "Hello Jérôme Alves !"
>
> a = nil
>
> aReceiver.printSomething?("Jérôme", "Alves") //
> => aReceiver.printSomething still has a value, but it does nothing
>
>
> As you can see, if you call weakFunc() with a func which has multiple
> arguments, the T generic will be a tuple and I guess this is thanks to this
> "implicit tuple splat" feature but I'm not sure.
> So can someone enlighten me ? Will this code continue to work if this
> proposal is approved ?
>
>
> Le 5 févr. 2016 à 19:12, Joe Groff via swift-evolution <
> swift-evolution at swift.org> a écrit :
>
> Hello Swift community,
>
> The review of “Remove implicit tuple splat behavior from function
> applications” begins now and runs through February 9, 2016. The proposal is
> available here:
>
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0029-remove-implicit-tuple-splat.md
>
>
> Reviews are an important part of the Swift evolution process. All reviews
> should be sent to the swift-evolution mailing list at
>
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
> or, if you would like to keep your feedback private, directly to the
> review manager. When replying, please try to keep the proposal link at
> the top of the message:
>
> Proposal link:
>
>
> http://github.com/apple/swift-evolution/blob/master/proposals/0029-remove-implicit-tuple-splat.md
>
> Reply text
>
> Other replies
>
>
> *What goes into a review?*
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> answer in your review:
>
> • What is your evaluation of the proposal?
> • Is the problem being addressed significant enough to warrant a change to
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>
> More information about the Swift evolution process is available at
>
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>
>
> Thank you,
>
> -Joe
> Review Manager
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