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Elixir combines aspects of Erlang, Clojure and Ruby to provide immutable data structures, high-order functions, pattern matching, and concurrency features like lightweight processes and message passing. The document discusses Elixir concepts like immutability, collections, functions, composition, concurrency and tooling like IEx, Mix, ExUnit and Dialyzer. It also covers Erlang concepts like ETS, Erlang Top and built-in term storage that Elixir inherits from Erlang.
![Immutability
animals = ["capybara", "apple", "lemur"]
List.delete(animals, "apple")
#=> ["capybara", "lemur"]
animals
#=> ["lion", "table", "bear"]](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-4-320.jpg){kind=tracking}
![High-order functions
double = fn(i) -> i * 2 end
Enum.map([1, 2, 3], double)
#=> [2, 4, 6]](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-5-320.jpg){kind=tracking}
![Pattern matching
[first, second, _] = [
:virginia,
:singapore,
:ireland,
]
first
#=> :virginia
second
#=> :singapore](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-6-320.jpg){kind=tracking}
![Pattern matching
list = [1, 2, 3]
[1 | tail] = list
tail
#=> [2, 3]
[2 | _] = list
** (MatchError) no match of right hand side
value: [1, 2, 3]](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-7-320.jpg){kind=tracking}
![Collections
Enum.any?(["foo", "bar", “hi"],
fn(s) -> len(s) == 2 end)
#=> true
File.read("path/to/unknown/file")
#=> {:error, "reason"}
map = %{:foo => "bar", :hello => "hi"}
map[:foo]
#=> “bar"](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-8-320.jpg){kind=tracking}
![Functions
def square([]), do: []
def square([head | tail]) do
[head * head | square(tail)]
end
square([1, 2, 3])
#=> [1, 4, 9]
Enum.map([1, 2, 3], fn(x) -> x * x end)
#=> [1, 4, 9]](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-9-320.jpg){kind=tracking}
![Supervisor
children = [
supervisor(Stats.Supervisor),
supervisor(Queue.KafkaSupervisor),
worker(Queue.SQSWorker, [period, []]),
supervisor(Queue.Supervisor),
supervisor(Cache.DBSupervisor),
Plug.Adapters.Cowboy.child_spec(:http, Router, [],
[port: port])
]
supervise(children,
strategy: :one_for_one,
max_restarts: 10,
max_seconds: 1
)](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-14-320.jpg){kind=tracking}
![Worker
def handle_cast(:receive, state) do
case :sqs.receive(state.queue) do
[] -> Logger.info("no messages")
messages -> to_kafka(messages)
end
{:noreply, state}
end
def terminate(reason, _) when reason == :normal, do: :ok
def terminate(reason, state) do
Logger.error("#{reason}: #{inspect state}")
:ok
end](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-15-320.jpg){kind=tracking}
![Type Specifications
@spec network(integer) :: {String.t, String.t} | :not_found
def network(id) do
case :ets.lookup(:db_networks, id) do
[{^id, name, url}] -> {name, url}
_ -> :not_found
end
end
Dialyzer is a static analysis tool that identifies software
discrepancies such as type errors, unreachable code,
unnecessary tests, etc in Erlang / Elixir applications.](https://image.slidesharecdn.com/pn-tracker-160408082335/85/PubNative-Tracker-20-320.jpg){kind=tracking}
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- 3. Elixir is what would happen if Erlang, Clojure and Ruby somehow had a baby and it wasn't an accident. Devin Torres open source enthusiast
- 4. Immutability animals = ["capybara", "apple", "lemur"] List.delete(animals, "apple") #=> ["capybara", "lemur"] animals #=> ["lion", "table", "bear"]
- 5. High-order functions double = fn(i) -> i * 2 end Enum.map([1, 2, 3], double) #=> [2, 4, 6]
- 6. Pattern matching [first, second, _] = [ :virginia, :singapore, :ireland, ] first #=> :virginia second #=> :singapore
- 7. Pattern matching list = [1, 2, 3] [1 | tail] = list tail #=> [2, 3] [2 | _] = list ** (MatchError) no match of right hand side value: [1, 2, 3]
- 8. Collections Enum.any?(["foo", "bar", “hi"], fn(s) -> len(s) == 2 end) #=> true File.read("path/to/unknown/file") #=> {:error, "reason"} map = %{:foo => "bar", :hello => "hi"} map[:foo] #=> “bar"
- 9. Functions def square([]), do: [] def square([head | tail]) do [head * head | square(tail)] end square([1, 2, 3]) #=> [1, 4, 9] Enum.map([1, 2, 3], fn(x) -> x * x end) #=> [1, 4, 9]
- 10. Composition defmodule Math do def sum(a, b) do a + b end end Math.sum(1, 2) #=> 3
- 12. Concurrent processes with no data sharing provide a strong measure of fault isolation. A software error in a concurrent process should not influence processing in the other processes in the system. creator of Erlang Joe Armstrong
- 13. Based on its designated behavior, the actor responds to incoming messages by send new messages, spawn new actors and/or changing its future behavior. Each actor has its own mailbox and isolated state.
- 14. Supervisor children = [ supervisor(Stats.Supervisor), supervisor(Queue.KafkaSupervisor), worker(Queue.SQSWorker, [period, []]), supervisor(Queue.Supervisor), supervisor(Cache.DBSupervisor), Plug.Adapters.Cowboy.child_spec(:http, Router, [], [port: port]) ] supervise(children, strategy: :one_for_one, max_restarts: 10, max_seconds: 1 )
- 15. Worker def handle_cast(:receive, state) do case :sqs.receive(state.queue) do [] -> Logger.info("no messages") messages -> to_kafka(messages) end {:noreply, state} end def terminate(reason, _) when reason == :normal, do: :ok def terminate(reason, state) do Logger.error("#{reason}: #{inspect state}") :ok end
- 16. tooling
- 17. IEx iex(1)> Weather ...(1)> |> where(city: "Berlin") ...(1)> |> order_by(:temp_lo) ...(1)> |> limit(10) ...(1)> |> Repo.all
- 19. ExUnit test "decodes a base64 without padding chars" do assert Token.urlsafe_decode64("YWJjZA") == "abcd" assert Token.urlsafe_decode64("YWJjZA=") == "abcd" assert Token.urlsafe_decode64("YWJjZA==") == "abcd" end ➜ tracker mix test test/tracker/api/token_test.exs --trace Tracker.API.TokenTest * decodes a base64 without padding chars (8.1ms) * decodes a base64 in the URLEncoding mode defined in RFC 4648 (0.01ms) * fixes a token with a double question mark (0.01ms) * decrypts a token (15.2ms) * returns error with a broken token (14.8ms) Finished in 0.1 seconds (0.09s on load, 0.03s on tests) 5 tests, 0 failures
- 20. Type Specifications @spec network(integer) :: {String.t, String.t} | :not_found def network(id) do case :ets.lookup(:db_networks, id) do [{^id, name, url}] -> {name, url} _ -> :not_found end end Dialyzer is a static analysis tool that identifies software discrepancies such as type errors, unreachable code, unnecessary tests, etc in Erlang / Elixir applications.
- 21. $ iex --name console@127.0.0.1 --remsh tracker@127.0.0.1 etop Erlang Top is a tool for presenting information about Erlang processes similar to the information presented by "top" in UNIX. erlang.processes() Returns a list of process identifiers corresponding to all the processes currently existing on the local node. erlang.memory() Returns a list with information about memory dynamically allocated by the Erlang emulator.
- 22. Built-In Term Storage ETS tables are implemented as BIFs in the ets module. The main design objectives ETS had was to provide a way to store large amounts of data in Erlang with constant access time and to have such storage look as if it were implemented as processes in order to keep their use simple and idiomatic.