[swift-evolution] SE-0111 and Curried argument labels: Unintended Consequences

[T.J. Usiyan]

I noticed this immediately and assumed that it was recognized as suboptimal
but tolerable for now. The required underscores were meant to leave space
for improvement in this regard, no? If not… sad face.

TJ

On Tue, Oct 4, 2016 at 12:21 PM, Erica Sadun via swift-evolution <
swift-evolution at swift.org> wrote:

> SE-0111 established that Swift's type system would not allow function
> argument labels to be expressed as part of a function type. As I've been
> working with curried functions, I'm discovering an unintended consequence
> of this proposal in that it strips curried functions of their external
> labels and the resulting calls of their readability.
>
> ```
> public func projected(
>     function f: @escaping (CGFloat) -> CGFloat) ->
>     (_ p0: CGPoint, _ p1: CGPoint) ->
>     (_ percent: CGFloat) -> CGPoint
> {
> ```
>
> Calling the first level of currying still reads acceptably:
>
> ```
> let projectedFunction = projected(function: fToApply)
> ```
>
> But after that, the enforced label-less arguments mean all further
> semantics have to stay within the name of the assigned partially applied
> function symbol and all arguments must be supplied without meaning, which
> is not in the spirit of API guidelines or under the umbrella of Swiftiness:
>
> ```
> let fixedFunction = projectedFunction(p0, p1)
> let value = fixedFunction(0.2)
> ```
>
> There's no way to give either the line segment start and end points or the
> percent-of-progress arguments any labels.  Further, Xcode/QuickHelp does
> not provide any support for documenting the roles of each curried return
> type.
>
> Could this be addressed specifically for currying or has the boat sailed
> forever on this topic?
>
> -- E
>
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20161004/a3007e11/attachment.html>