[erlang-questions] maps:first

[dmkolesnikov@REDACTED]

Hello,

May be my comment is not extremely relevant to this discussion but

I would wish that Erlang data structures supports zipper trait. It make easy to iterate them back and force.

Dmitry 

> On 13 Aug 2019, at 21.18, Oliver Bollmann <oliver.bollmann@REDACTED> wrote:
> 
> Hi,
> 
> i guess we do all the same,
> 
> 1) processes with propery Y, i have about 1-10 million processes
> 2) gen_server to manage these processes in maps,dict,lists for example a pool with in,out,leave,delete
> 3) monitoring these processes
> 
> Dilemma: 
> 
> If process P died i have to delete it from data structure using in 2)
> 
> - maps, dict very fast; 
>    lists -> List -- [Item] slow!
>    OK, i could use a sorted list and and the subtract would be faster, but insert is then slower!
>    And subtract need an algorithm!
> 
> - i do not want a special process, only one random or the first one from data structure using in 2)
>    here is the place where i need first_from_data_structure
>    lists very fast: first defines it itself -> [First|Rest] = List,
>    but using maps or dict there is not first, at all!
> 
> The question is: How can i get a random or first item from maps or dict?
> 
> Hope that helps!
> 
> Oliver             
> 
> 
> 
>> On 13.08.19 15:41, Lukas Larsson wrote:
>> 
>> 
>>> On Tue, Aug 13, 2019 at 3:34 PM Oliver Bollmann <oliver.bollmann@REDACTED> wrote:
>>> I often need maps:first(Map), is there plan for it?
>>> 
>> 
>> No, there is currently no plan for it, as I cannot think of a use case when it would be useful, but that might just be poor imagination on my part.
>> 
>> What do you use maps:first for?
>>  
>>> My current implementation is: 
>>> 
>>> first(Map) ->
>>>   case maps:next(maps:iterator(Map)) of
>>>     {Key,Val,_} -> {Key,Val};
>>>     none -> none
>>>   end.
>>> 
>>> Create the iterator always a new map?
>>> -- 
>>> Grüße
>>> Oliver Bollmann
>>> _______________________________________________
>>> erlang-questions mailing list
>>> erlang-questions@REDACTED
>>> http://erlang.org/mailman/listinfo/erlang-questions
> -- 
> Grüße
> Oliver Bollmann
> _______________________________________________
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