what is the closest thing to Arrays in Elixir. By arrays I mean, a container for values which I can access in constant time. I’ve looked at tuple, but according to the documentation : Tuples are not meant to be used as a “collection” type (which is also suggested by the absence of an implementatio…

For what you describe a tuple actually seems like a good choice. Some questions though: How many elements in this “array”? How static is this “array” to be? Is it to be globally accessed or through one process? When randomly picking a process is it enough just to generate a random number and use t…

You’re probably looking for List . You could then do something like this to grab a random entry: [1,2,3] |> Enum.take_random(1)

Unfortunately this will traverse list linearly. I’m looking for constant time lookup.

You can use a map, and periodically pick a random key ?!

There is also Keyword, but the order of the key is not preserved over 32000 keys… and they act as List, so there is no constant time access. For your use case, I would probably choose a map.

[image] anurag.peshne: What I actually want to do: I want to store n processes in an array and periodically pick a random process and send it a message. Does order matter? Do you need to access items by key or just at random? Map has been mentioned, but there is also MapSet if you don’t nee…

You may want to elaborate on your use case. Various datastructures (including arrays) have various performance characteristics for different kinds of operations and without knowing what operations you have in mind, it’s hard to recommend the best approach. Tuples have constant lookup time, but have…

[image] kokolegorille: There is also Keyword, but the order of the key is not preserved over 32000 keys… and they act as List, so there is no constant time access. This seems wrong. A keyword list is just a list, and lists preserve their order at all sizes.

@benwilson512 Yes You are right, it’s map which doesn’t keep order over 32 keys… I have been mixing up, both types and numbers :frowning:

Ah yeah. For maps it’s best to treat them as if they have no order at all, the fact that they happen to preserve order under 32 keys is explicitly just an artifact of how the algorithm works and should never be relied upon.

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Arrays

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anurag.peshne September 23, 2017, 11:43pm 5

Yes, that’s the last resort. I just want to make sure I’m not missing any data structure.