[swift-evolution] [Proposal]Make .map return the calling collection type

[Dmitri Gribenko]

On Tue, Apr 12, 2016 at 1:55 AM, Yogev Sitton via swift-evolution
<swift-evolution at swift.org> wrote:
> Map is great for transforming an array of objects - it is very useful and I use it a lot.
> I would love to use Map with Dictionaries and other collections as well.
>
> As an example - let’s say I have a dictionary [String : Person] - that maps a person to an ID.
> I want to use the map function a get a [String : String] - a dictionary that maps a person’s name to an ID.
> Currently - the map method is defined to always return an array so that is not possible to do.

Hi,

We can discuss adding special-case functions to individual collections
where it makes sense, but it does not make sense to do it for
collections in general, please see
https://github.com/apple/swift/blob/master/docs/StdlibRationales.rst#high-order-functions-on-collections-return-arrays
for the rationale.

Dmitri

-- 
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