[swift-evolution] [Draft] Dictionary & Set Enhancements

[Ricardo Parada]

Some thoughts after reviewing it a second time:

I am not sure I like having global functions first(_:_:) and last(_:_:).  Would it be possible to default the closure to do what last(_:_:) would do?  I'm assuming the most popular thing to do is to have the values from the second dictionary prevail. 

// These two would be equivalent to passing last(_:_:) function
let newDict = dict1.merged(with: dict2)		
let newDict = dict1.merged(with: dict2) { $1 }		

If someone wanted to do what first(_:_:) would do, or some other algorithm then it would be quite simple, wouldn't it?  For example:

// This would be equivalent to passing in the first(_:_) function
let newDict = dict1.merged(with: dict2) { $0 }		

// Combine values of common keys by adding them
let newDict = dict1.merged(with: dict2) { $0 + $1 }		





> On Apr 1, 2017, at 3:58 PM, Nate Cook via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Yep, here it is -- didn't realize the length would cause such problems!
> 
> 	https://gist.github.com/natecook1000/4bd8f20736eb99ed3c5a4cdcc41e9a5f <https://gist.github.com/natecook1000/4bd8f20736eb99ed3c5a4cdcc41e9a5f>
> 
> Nate
> 
>> On Apr 1, 2017, at 12:01 PM, Jason Gregori via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> I really like the merging methods and have already needed to write my own. Zach, do you mind showing a comparison of what you're thinking? 
>> 
>> Nate, do you mind throwing this up in a gist or something? My email client isn't letting me see the whole thing. 
>> 
>> Thanks, 
>> Jason
>> 
>> 
>> On Fri, Mar 31, 2017 at 11:52 AM Zach Waldowski via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> Snipped quoted proposal so as to not break the mailing list… By and large, I'm in favor. I like the potential for bringing up Dictionary and Set up to the implementation quality of Array and String.
>> 
>> I don't think `init(merging:resolvingCollisionsWith:)` et al hold their weight for inclusion in the language, unless some notable optimization opportunity can be surfaced out of it. Users frustrated at the lack of a `merge` in Swift want it to be opinionated and "just do the right thing," i.e., the same way as whatever other language they most recently used. A properly annotated and indented-to-be-beautiful use of the closure-based version will take up the same amount of code as doing the merge by hand with your custom condition. 
>> 
>> Sincerely,
>>   Zachary Waldowski
>>   zach at waldowski.me <mailto:zach at waldowski.me>
>> 
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