vrod
this is a question of the computer science. Is Elixir map a hash table? Or is it a keyword list having unique keys? I ask this because of the shape of Enum functions looking the same… for example fn {key, value} -> ... end looks same for maps and keyword lists
How is map stored in memory? Is getting a key O(1) operation in Elixir map? Is getting a key O(n) operation in Elixir list?
Where Next?
Trending in Questions
Other Trending Topics
Latest on Elixir Forum
Sponsor Spotlight
At WyeWorks, we believe great software is built by combining technical excellence with genuine human connection
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #library
- #deployment
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #elixirconf
- #channels
- #exunit
- #discussion
- #code-sync
- #podcasts
- #javascript
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ai
- #ecto-query
- #elixirconf-us
- #blog-post
- #elixir-ls
- #phoenix_html
- #iex
- #graphql
- #genstage
- #websockets
- #supervisor
- #advent-of-code
- #distillery
- #processes
- #elixirconf-eu
- #api
- #forms
- #metaprogramming
- #hex
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
Catch errors, track performance, monitor hosts and more.
Error tracking, logs, uptime, and Just Enough APM. Built for developers.
Elixir, Erlang & BEAM conferences from Code Sync - join us in 2026!
Practical resources that improve the lives of professional developers.
Bringing learning, work and compliance together since 1987.
The deployment platform built for Elixir: PaaS ease, VPS control.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"
Showing Posts 1 to 3- Show Best Posts
- Show All (oldest first)
- Show All (newest first)
LostKobrakai
Maps are stored either as hash map or as tuple (when small enough). Keyword lists are normal linked lists with
{atom, term}for all items.Enumfunctions work with any value implementingEnumerable.t. Datatype specific functions are inMap,KeywordorList.vrod
Thank you!
Qqwy
If you want to take a deep-dive in how maps are implemented internally, I recommend the blog article Breaking Erlang Maps by @jlouis. Small maps are stored as a ‘flatmap’: a sorted array of keys + their values. Big maps are stored as a ‘hash-array mapped trie’, which allows them to be persistent data structures (in a snippet like
x = %{a: 1, b: 2, c: 3}; y = Map.put(x, :b, 4)we do not have to copy the fields ofxto constructybut can re-use all unchanged fields ofxdirectly).