kpanic
Accessing a map element and adding parens after it might be confusing?
Hi,
I discovered by accident last week this:
Example:
quote do %{hello: "test"}.hello() end == quote do %{hello: "test"}.hello end
true
I get that the AST is the same – with parens or the absence of parens, however why this is an allowed syntax?
Thanks
Marked As Solved
OvermindDL1
Not just you, but sometimes that ambiguity lets you override things too. At one time we had tuple calls too that worked like {SomeModule, whatever, else, you, want} and if you did blah = {SomeModule, whatever, else, you, want} then did blah.bloop(42) then it ended up calling SomeModule.bloop(42, {SomeModule, whatever, else, you, want}), which was crazy useful for emulating first-class modules on the BEAM, but thanks to recent developments that is now broken… 
Yep, exactly this.
Conceptually this:
a.b
# expands to:
:"."(a, b)
# expands to:
case a do
mod when is_atom(mod) -> apply(mod, b, [])
%{} -> apply(:maps, :get, [b, a, nil])
# among some other things
end
Also Liked
gregvaughn
I suspect this is a transitory concern. I suspect you’re coming from an OO world (like most) where it is common to call methods on objects. As a functional language, Elixir has no methods at all. It’s functions. This . syntax just looks like a method/member access, but it’s really a function. Once you’ve spent more time with Elixir and internalized this information, the confusion should subside.
OvermindDL1
Eh, technically it is a function call, it lowers down to become :maps.get(:hello, %{hello: "test"}). On the beam VM there is no such thing as a map extraction operator like ., rather you can extract only by matching out the value via a hardcoded key or by calling the built in internal functions in the :maps module, and Elixir lowers to them.
kpanic
Thanks to everyone, hope this thread will be useful to someone else.
I marked @OvermindDL1 post as “solution” because it contains also the explanation of @gregvaughn and it’s not possible to mark multiple solutions
Popular in Questions
Other popular topics
Latest on Elixir Forum
Sponsor Spotlight
Producing high quality Elixir screencasts since 2017.
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.
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!"