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

[Federico Carrone]

It would be awesome to have a a map iterator/map comprehension.

On Tue, Apr 19, 2016 at 5:30 PM Robert Virding <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> 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>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.
>>
>>
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