[swift-evolution] [Pitch] Add `mapValues` method to Dictionary

Haravikk swift-evolution at haravikk.me
Tue May 24 06:36:19 CDT 2016

> On 24 May 2016, at 11:50, Brent Royal-Gordon <brent at architechies.com> wrote:
>> For this the key/value pair constructor for Dictionary would be the better option, since the .map() method essentially already lets you do this. Adding key transformation to .mapValues() would only make it less specialised (it’s called .mapValues after all ;), plus it would be incompatible with any simultaneous/future lazy implementation since you can’t just transform the keys lazily (you also need a way to transform them back if you intend to use them for lookups).
> He was suggesting the transform be of type (Key, Value) -> NewValue; that is, it would be able to see what the key was, but it wouldn't be able to transform the key.

Whoops right you are, sorry! Hmm, in that case, any examples that need the key for the transformation? I usually view keys as arbitrary, so needing them for this seems a little strange (hence my misunderstanding, at least that’s the reason I’m going to stand by in favour of “I can’t read” ;)

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