vals
iex(5)> list1 = [1,2,3]
[1, 2, 3]
iex(6)> list2 = [4 | list1]
[4, 1, 2, 3]
I am trying to imagine how immutability works in Elixir (and in other functional languages).
When line 6 is executed there will be no new list data structure created but both list1 and list2 will refer to the same underline data structure. Is it correct assumtion???
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
- #ecto-query
- #elixirconf-us
- #blog-post
- #ai
- #elixir-ls
- #phoenix_html
- #iex
- #graphql
- #genstage
- #websockets
- #supervisor
- #advent-of-code
- #distillery
- #processes
- #api
- #forms
- #hex
- #security
- #metaprogramming
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.
Master modern tools, write cleaner code, and tackle real-world challenges.
**Building the future of software with AI, trust, and human connection.**
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)
gregvaughn
Yes. In your example you’ll have a single linked list in memory, but the different variables will point to different head elements of it. Since it is a singly linked list there is no way from the
list1variable to ever go “backwards” and see element “4”.In a general hand-wavey sense, this is how a lot of data structures work in immutable languages. You basically have one large/combined structure and different variables have different visibility to parts of it.
vals
However, ignoring the under-the-hood implementation, the end user of the language should be under the impression that a brand new copy of the list is created. The particular implementation shown is just a trick for the sake of efficiency.
Joseph
I’m not so sure that it’s about copying as much as it is that immutability gives us the effect that it’s like copying. As you say, it’s like that underneath for efficiency, but the interesting thing is that if we have immutable data then we don’t have to copy underneath: we know that pointing to different parts of the data (from different variables) won’t give us a different value at different times.