[swift-evolution] Remove forEach?

[Chris Eidhof]

Would it make sense to explore this approach a bit further? Or will it be out of scope for Swift 3 anyway? This could also enable a lot of other cool stuff. To me, it feels like a big task, so not sure how to proceed on this...

Chris

> On 09 Dec 2015, at 12:01, Joe Groff <jgroff at apple.com> wrote:
> 
> 
>> On Dec 9, 2015, at 8:47 AM, David Owens II <david at owensd.io <mailto:david at owensd.io>> wrote:
>> 
>> Another language construct seems a bit much for this, right? Maybe I’m missing something, but can’t we get the same behavior with an overload?
> 
> A language construct that helps eliminate multiple other language constructs would potentially be a net win, though. If there were closures that supported nonlocal exits, then `do`, `for...in`, and possibly other constructs could become library functions, and other "block-like" library features like `autoreleasepool`, `withUnsafePointer` would work more naturally too.
> 
> -Joe
> 
>> extension Array {
>>     func forEach<U>(body: (element: Element) throws -> U?) rethrows -> U? {
>>         for e in self {
>>             if let result = try body(element: e) { return result }
>>         }
>>         
>>         return nil
>>     }
>> }
>> 
>> func g(e: Int) -> Int? {
>>     if e == 2 { return e }
>>     return nil
>> }
>> 
>> let arr = [1, 2, 3]
>> arr.forEach { print($0) }
>> let result = arr.forEach(g)
>> result                           // has the value of 2
>> 
>> 
>> Now, Swift has some issues determining the types properly if you attempt to inline the g function at the forEach() callsite, but that can be fixed.
>> 
>> -David
>> 
>>> On Dec 9, 2015, at 4:40 AM, Stephen Celis via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>>> On Dec 8, 2015, at 5:13 PM, Joe Groff via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>> 
>>>> Another direction you might take this is to make it a type annotation on the function type, like throws, so forEach has a type like this:
>>>> 
>>>> func forEach(body: (Element) breaks -> ())
>>>> 
>>>> and a closure that `breaks` has nonlocal behavior for break/continue/return (and is implied to be noescape and void-returning, I guess).
>>> 
>>> This is really interesting. Ruby provides similar functionality with its lambda vs. proc, but a type annotation is much more understandable. It could also imply @noescape automatically:
>>> 
>>>    func forEach(@canbreak body: Element -> Void)
>>> 
>>> Stephen
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>> 
> 

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