[swift-evolution] [Pitch] Improve `init(repeating:count)`

[Tony Allevato]

Couldn't this be rewritten more simply today as:

    Array((0..<3).map { index in MyView(forIndex: index) })

And the version that doesn't need the index could be written:

    Array((0..<3).map { _ in UIView() })

The AnyIterator approach posted above is also nice—I wouldn't have thought
of that one. But I suppose that only works in the case where you don't need
the index.

So the question is, should we increase the API surface of Array for
something that (IMO) is already fairly straightforward to do? The nice
thing about the approaches above is that they're composable. Array doesn't
have to make any assumptions about closures or index arguments to those
closures; it just takes a sequence and we already have primitives to
construct sequences of new objects using .map. Array(repeating:count:) and
repeatedElement(_:count:) are nice when the value being repeated is fixed,
but I think once you start getting into questions like "what if I need a
different thing each time?" or "what if I need to involve the index as part
of the elements?" then it's better suited to compose the features already
there to build something up than to add new APIs that try to cover each of
these special cases.


On Thu, Aug 17, 2017 at 8:40 AM Christopher Kornher via swift-evolution <
swift-evolution at swift.org> wrote:

> We might as well add the index to the call so elements can be created from
> other lists, etc.
>
>  Array(repeatedlyCalling: { (index:Int) in MyView( forIndex:index ) },
> count: 3) // This might by syntactically correct...
>
>
>
> On Aug 17, 2017, at 9:24 AM, Rob Mayoff via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> On Thu, Aug 17, 2017 at 7:04 AM, Robert Bennett via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> Alternatively, instead of replacing the current definition with an
>> autoclosure version, we could leave the current version in place and add a
>> version taking a function. This could be especially useful when you’ve
>> defined a function like `makeMySpecialKindOfButton() -> UIButton` that does
>> a lot of customization to an object before returning it.
>>
>> Array(repeating: { return UIView() }, count: 3)
>> and
>> Array(repeating: makeMySpecialKindOfButton, count: 3)
>>
>
> This is still source-breaking, because an array of closures is legal. We
> need a different name to avoid breaking source:
>
>     Array(repeatedlyCalling: { UIView() }, count: 3)
>
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