Code maintainability and comprehension for decent multi-core performance on a stable VM.
I rarely get that sinking feeling of technical debt
i.e. oh crap why am I doing this… this is going to be hard to maintain or change 10 years from now.
As a part-time programmer and business manager, Elixir is incredibly refreshing to write and maintain systems with.
I was already in love with pattern matching from other languages. That stuff is seriously addicting. Like no turning back addicting.
I started a new job and Elixir was the only language in a list of pre-approved languages to write new stuff in.
Honestly…what blew my mind the most was realizing that this is what Akka is emulating. Except this is the real deal. No more messing with ExecutionContexts or defining huge nests of case classes. Or worrying about Haskellisms.
I love Elixir. It’s scratching every itch.
One silly thing that really surprised me (coming from a Java World a while ago…) was this simple snippet:
raise_msg = &"Ooooops... something went wrong! Something: #{inspect(&1)}"
# some logic and then...
raise raise_msg.("bad thing")
Maybe this is common to Rubists and the like but it’s simple and I like it.
The first thing that shocked me on the BEAM was the fridge example in Learn You Some Erlang for Greater Good. It was that moment when light weight processes made sense and from there to gen_servers was easy. This is still my recommendation when someone is new to the BEAM (although it is written in erlang, it is really well written and easy to follow…).
Here is the final code that made me understand how to deal with mutable state using processes in an immutable language with recursion:
-module(kitchen).
-compile(export_all).
start(FoodList) -> spawn(?MODULE, fridge2, [FoodList]).
store2(Pid, Food) ->
Pid ! {self(), {store, Food}},
receive
{Pid, Msg} -> Msg
after 3000 ->
timeout
end.
take2(Pid, Food) ->
Pid ! {self(), {take, Food}},
receive
{Pid, Msg} -> Msg
after 3000 ->
timeout
end.
fridge2(FoodList) ->
receive
{From, {store, Food}} ->
From ! {self(), ok},
fridge2([Food|FoodList]);
{From, {take, Food}} ->
case lists:member(Food, FoodList) of
true ->
From ! {self(), {ok, Food}},
fridge2(lists:delete(Food, FoodList));
false ->
From ! {self(), not_found},
fridge2(FoodList)
end;
terminate ->
ok
end.
There are a lot of features of Elixir that are great, but this is probably the first thing I would mention as well. It’s amazing how much code this feature alone can clear up.
Another thing that impresses me is how fast new versions of Elixir are released. I feel like it wasn’t even that long ago I got the Programming Elixir 1.2 book and now the 1.6 book is out, but 1.8 is the latest version 
It blows my mind how much you can learn about good software practices by reading the debates here, watching Elixir conferences or taking a course on elixir.
Something like that:
defmodule MyMind do
@moduledoc "Simplified implementation of my mind on timeline!"
@date_join ~D[2016-05-11]
@doc "Not sure how much extra online English lessons affects those results …"
@spec at(Date.t()) :: String.t()
def at(date), do: date |> Date.compare(@date_join) |> do_at()
defp do_at(:lt), do: "I think … I'm … fine … thank you …"
defp do_at(_), do: "Yo bro! I'm great, thanks! And you?"
end
btw. Last time I tried to properly remind my past, but I hit such error:
Exception in thread "main" java.lang.StackOverflowError
at java.io.PrintStream.write(PrintStream.java:480)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:221)
at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:291)
at sun.nio.cs.StreamEncoder.flushBuffer(StreamEncoder.java:104)
at java.io.OutputStreamWriter.flushBuffer(OutputStreamWriter.java:185)
at java.io.PrintStream.write(PrintStream.java:527)
at java.io.PrintStream.print(PrintStream.java:669)
at java.io.PrintStream.println(PrintStream.java:806)
at MyMind.recursiveRemindPast(MyMind.java:65505)
at MyMind.recursiveRemindPast(MyMind.java:65535)
at MyMind.recursiveRemindPast(MyMind.java:65535)
at MyMind.recursiveRemindPast(MyMind.java:65535)
...
Looks like there is still lots of work for me! 
reduce is god. Didn’t really sink in until I started using a functional language for real.
Macros are fine, but macros calling other macros still makes my head hurt.
Pattern matching is the thing I miss most when working with other langs.
Erlang/OTP is mind-blowing to me. However, if there’s no Elixir, I probably never actually take a serious look at them (although it was always on the todo list). I can raise some examples:
I realized the scheduling efficiency is much more important than execution speed:
Given Java is much faster than Erlang – Erlang is much faster than Java is most of the Web and other scenarios. The nature of most user-oriented scenarios is about unordered events and operations.
Erlang vs Java is more like agile vs waterfall. If the requirement never changes probably waterfall is better, just like scientific calculation or batch operations. But more scenarios are dynamic, react to change is far more important than personal efficiency.
I realized programming language is probably is not enough. We need operating systems. Processes. Applications. Isolation.
Typically most of the libraries run on your threads, in typical programming languages. If one of them crashes, everything crashes unless you handle them.
In typical language: two objects, one is saying ‘hi’ to another, and another responds with something the former does not understand. The whole world explodes. That’s crazy! And yet we’re so used to them.
In typical operating system, if there are some application crashes, people is not expecting the whole operating system crashes. They’ll be really pissed if it does.
Your database and your application could be the same thing.
Actor is similar to this philosophy, and riak_core / lasp / o(e)rleans are stepping toward this direction. It’s not popular or easy to handle right now, but we will eventually be there. The database is always ‘the’ problem that makes me really think ‘there should be a much better’ way. After I read these solutions, I believe there’s a bright future for this philosophy.
They are really mind-blowing.
SICP and Lisp blew my mind on how to write software.
Erlang/OTP blew my mind on how to run software. And running software properly is so important nowadays.