[swift-evolution] Remove forEach?

[Joe Groff]

> On Dec 9, 2015, at 8:47 AM, David Owens II <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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