Elixir: Concurrent and Fault-Tolerant Functional Programming
BEAM VM and Process Model
Elixir runs on BEAM (Bogdan/Barłog Erlang Abstract Machine). Erlang: telecommunications system (99.9999999% uptime, 9 nines reliability). BEAM designed for fault tolerance: "let it crash" philosophy. Supervisor tree: monitors processes, restarts on failure. Process: lightweight abstraction (not OS thread). spawn(() -> IO.puts("hello")) creates process (~500 bytes memory). 262K concurrent processes feasible on standard hardware (vs 100s of OS threads). Message passing: actors communicate via mailbox. send(pid, {:greet, "World"}) sends message. Process receives: receive do { :greet, name} -> IO.puts("Hello #{name}") end. Pattern matching: selectively match messages. Distributed: BEAM supports clustering (multiple nodes). RPC: call functions on remote node. Fault tolerance: if process crashes, supervisor restarts (transparent to caller).
Pattern Matching and Immutability
Pattern matching: elegant data extraction. {name, age} = {"John", 30}. Destructuring: case user do { :ok, data} -> ..., { :error, reason} -> ... end. Wildcard: _ matches anything (ignored). Pinning: ^age restricts match (match if age equals current value). Guards: when name != "" (conditions in patterns). Example: def greet({ name, age }) when age > 18, do: "Welcome, #{name}". List patterns: [head | tail] = [1, 2, 3] (head=1, tail=[2,3]). Recursion via pattern matching: def length([]), do: 0; def length([_|tail]), do: 1 + length(tail). Immutability: all data immutable (modifications return new copy). list = [1, 2, 3], new_list = [0 | list] (prepend, original list unchanged). Pipes: |> passes result to next function. "hello" |> String.upcase() |> String.split("") (readable, functional style).
Phoenix Framework and Web Development
Phoenix: high-performance web framework (benchmark: 2M+ requests/second simple endpoint). Router: pipeline-based request processing. scope "/api", ApiController do get("/users", :index); post("/users", :create) end. Plugs: middleware components. plug :authenticate before :index (auth runs before index action). Connection: %Conn{} carries request/response state through pipeline. Ecto: database ORM. schema "users" do field :name, :string; field :email, :string end. Changesets: validate data. changeset = User.changeset(user, params); Repo.insert(changeset). Relationships: has_many, belongs_to declarations. LiveView: real-time reactive UI (WebSocket-based). defmodule UserLive do use Phoenix.LiveView; def render(assigns), do: ~H"