> On Oct 26, 2016, at 22:23 , Dave Abrahams via swift-users
> <swift-users@swift.org> wrote:
>
>
> on Wed Oct 26 2016, Rick Mann <swift-users-AT-swift.org> wrote:
>
>> It seems fairly natural to want to do this:
>>
>> let bigDictionary = ...
>> let smallerDictionary = bigDictionary.filter { key, value in <some test
>> returning Bool> }
>
>> Similarly, it seems natural to want to map this way.
>
> It's reasonable for filter, but maybe not for map. Map follows certain
> laws, and one of them is that you get the same number of elements out as
> you put in. But you can easily map all keys to the same key, and the
> law would be violated.
Sure map would produce a dictionary of the same number of entries. I didn't
mean to imply map would also filter. But I'm basically transforming a JSON
dictionary into a new version of that dictionary with fewer elements. I'd like
to first filter it, then map it, and have the result be a dictionary.
--
Rick Mann
rm...@latencyzero.com
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