CODEWITHSUNDEEP
erlang
some_id
some_id

Reputation: 29896

Sorting a list in Erlang

How does one sort a list in Erlang depending on a tag for each element?

If I have a process which loops and receives a single value from multiple processes and then I want to arrange the list according to the tag(which is an index) as an element is received.

How does one do this without using BIFs?

I currently do the following but would like to arrange the list when an element is added, like an insertion sort using the tags.

fibLoop(calcData) ->
receive
 {Number, Tag} ->
 fibLoop([{Number, Tag}|calcData]);

Upvotes: 2

Views: 2307

Answers (2)

Daniel Luna
Daniel Luna

Reputation: 1979

There are multiple ways to do what you want, a bit depending on what you want to use the value for later.

Easy solution would be to use gb_trees. gb_trees are a sorted structure that you can loop over using an iterator.

Or if you want to keep it simple and have a list you could use orddict (or possibly ordsets).

orddict:store(Number, Tag, CalcData)

to insert {Number, Tag} into an ordered list. See documentation for orddict for more information.

To get the smallest value in the list you can use hd/1, and to get the biggest lists:last/1 (not that I recommend lists:last, mind you).

Upvotes: 2

Lukas
Lukas

Reputation: 5327

Something like this would probably work:

insert({_, Tag} = Data, [{_,HTag}|_] = List) when Tag >= HTag ->
  [Data | List];
insert(Data, [H | T]) ->
  [H | insert(Data, T)];
insert(Data, []) ->
  [Data].

Upvotes: 2

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