[erlang-questions] Wanted additions to the maps module?

[Björn-Egil Dahlberg XB]

On 2016-04-20 16:38, Federico Carrone wrote:
> It would be awesome to have a a map iterator/map comprehension.

Many are of the same opinion. However iterators are not in this scope. 
Only API additions to the maps module are.
Efficient iterators are necessary to implement efficient generators for 
maps. Efficient maps comprehension is whole other ballgame.

I will post a PR of maps:take/2 and maps:apply/3,4 later this week. I'm 
not sure about apply .. or it's name.


>
> On Tue, Apr 19, 2016 at 5:30 PM Robert Virding <rvirding@REDACTED 
> <mailto:rvirding@REDACTED>> wrote:
>
>     I missed this thread, but Björn-Egil you know what I want. :-)
>
>     maps:first(Map) -> {Key,Value} | error.
>     maps:next(Key, Map) -> {Key,Value} | error.
>
>     Robert
>
>
>     On 13 April 2016 at 15:40, Björn-Egil Dahlberg XB
>     <bjorn-egil.xb.dahlberg@REDACTED
>     <mailto:bjorn-egil.xb.dahlberg@REDACTED>> wrote:
>
>         There is currently no (good) way to get out of C-context to
>         execute some erlang snippet and then get back into c-context.
>         Traps does this but only in a controlled manner. I think it is
>         doable though.
>
>         Your proposal of maps_apply/3 is the maps equivalent of
>         dict:update/3 and sadly that name is already occupied in maps
>         (it's the equivalent of gb_trees).
>
>         I think we should add it to the API without thinking about the
>         performance too much. Performance can always be improved later on.
>
>         Is maps:apply/3 the best name we can think of? I don't really
>         trust you and naming things. =) update/3,4 would probably have
>         been best but c'est la vie.
>
>         // Björn-Egil
>
>
>         On 2016-04-13 13:09, Jesper Louis Andersen wrote:
>>
>>         On Fri, Apr 8, 2016 at 8:31 PM, Björn-Egil Dahlberg
>>         <wallentin.dahlberg@REDACTED
>>         <mailto:wallentin.dahlberg@REDACTED>> wrote:
>>
>>             Have you repeated some code or built your own private lib
>>             to handle certain maps specific tasks and thought "why
>>             isn't this in the maps module?"
>>
>>
>>         One function I like to have is "apply update via function",
>>         and I implement it somewhat often:
>>
>>         maps_apply(F, K, Map) ->
>>             V = maps:get(K, Map),
>>             maps:put(K, F(V), Map).
>>
>>         But it can be made much faster in a direct implementation
>>         since I don't have to first pick up the value: I can apply F
>>         when I sit with the value at hand and thus avoid the "put"
>>         lookup path. It might, however, be nasty to implement because
>>         F is in Erlang-context, whereas the maps operations are in
>>         BIF-context.
>>
>>
>>         -- 
>>         J.
>>
>>
>>         _______________________________________________
>>         erlang-questions mailing list
>>         erlang-questions@REDACTED <mailto:erlang-questions@REDACTED>
>>         http://erlang.org/mailman/listinfo/erlang-questions
>
>
>         _______________________________________________
>         erlang-questions mailing list
>         erlang-questions@REDACTED <mailto:erlang-questions@REDACTED>
>         http://erlang.org/mailman/listinfo/erlang-questions
>
>
>     _______________________________________________
>     erlang-questions mailing list
>     erlang-questions@REDACTED <mailto:erlang-questions@REDACTED>
>     http://erlang.org/mailman/listinfo/erlang-questions
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20160420/dfa3b509/attachment.htm>