mrkurt
Map over a map and create a new map?
Hello! I’m trying to get more comfy with idiomatic elixir, and it seems like one line anonymous fn {} -> ... end calls might not be ideal. Maybe they are, but I’m curious if there’s a cleaner way to do a map over a map and get another map.
Here’s what I have:
Enum.map(m, fn {k,v}-> {k, length(v)} end) |> Map.new
Is there a way to write this more concisely? At first I thought capture syntax might be the way, but I can’t find a function to capture that creates a tuple.
And for bonus points, can you destructure capture arguments? Because I also have one of these guys:
|> Enum.flat_map(fn {_, %{metas: metas}} -> metas end)
—edit—
For the second example, I came up with this (which does indeed make me happier):
|> Map.values
|> Enum.flat_map(&Map.get(&1, :metas))
Marked As Solved
sabiwara
Actually Map.new/2 accepts a function, so you can also directly call Map.new(m, fn {k,v}-> {k, length(v)} end).
Also Liked
kokolegorille
What about skipping the first Enum.map?
Map.new(m, & {elem(&1, 0), String.length(elem(&1, 1))})
You can also use for with reduce.
for {k, v} <- m, reduce: %{} do acc -> Map.put(acc, k, String.length(v)) end
or Enum.reduce directly
Enum.reduce(m, %{}, fn {k, v}, acc -> ... end)
kokolegorille
You might not have seen I used Map.new/2 in my reply 
sabiwara
Oh sorry I missed it!
Also worth noting, Map.new/2 should be the fastest option as well according to this benchmark.
Popular in Questions
Other popular topics
Latest on Elixir Forum
Sponsor Spotlight
Phoenix, LiveView, multimedia pipelines, distributed systems. 400 engineers, Elixir since 2017. Available for hire.
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
- #code-sync
- #javascript
- #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.
Develop your skills with books, videos, and courses.
Producing high quality Elixir screencasts since 2017.
Enabling companies to succeed by building software people love.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"