ollran
Pattern matching against arbitrary sized tuple
How can I pattern match against an arbitrary sized tuple? This works:
{status, _, _} = {:ok, 1, 2}
But what if I don’t know the structure of the tuple on the right side and I only care about the first element? This doesn’t work:
{status, _} = {:ok, 1, 2, 3, 4, 5, 6}
{status, _} = {:ok, {:random, :things}, [1, 2, 3]}
Is it possible to get the first value from the tuple with pattern matching?
Marked As Solved
NobbZ
No. A tuple is of fixed size.
You can either use status = elem({:ok, 1, 2, 3}, 0) or [status | _] = Tuple.to_list({:ok, 1, 2, 3}.
Also Liked
lpil
Tuple.to_list/1 will allocate a new list, Kernel.elem/2 can be used to retrieve the first element without creating this intermediate list 
glmeocci
I’d love it!
{:file_info, file_sieze | _the_rest_as_tuple} <- info
dkuku
would be handy to have some macro that generates the missing underscores:
{:ok, info} <- :file.read_file_info(pid),
{:file_info, file_size, _, _, _, _, _, _, _, _, _, _, _, _} <- info,
{:file_info, file_size, _escape_next(12)} <- info,
Popular in Questions
Other popular topics
Latest on Elixir Forum
Sponsor Spotlight
Supporting innovation across the BEAM ecosystem.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #deployment
- #library
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #channels
- #elixirconf
- #exunit
- #discussion
- #javascript
- #code-sync
- #podcasts
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ecto-query
- #elixir-ls
- #phoenix_html
- #iex
- #blog-post
- #graphql
- #genstage
- #ai
- #websockets
- #supervisor
- #advent-of-code
- #elixirconf-us
- #distillery
- #processes
- #forms
- #api
- #metaprogramming
- #security
- #performance
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Catch errors, track performance, monitor hosts and more.
Real-time error tracking, performance insights, and observability for devs.
Practical resources that improve the lives of professional developers.
Develop your skills with books, videos, and courses.
The deployment platform built for Elixir: PaaS ease, VPS control.
Courses that'll move you from confusion to "Aha, now I get it!"