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Elixir Flashcards (Basics)

Elixir Basics — Flashcards

30 flashcards covering core Elixir concepts. Tap a card to reveal the answer.

Additional Flashcard Topics

  • Pattern Matching: case, with, function heads. {:ok, value} = {:ok, 42} binds value to 42. Pin operator ^ matches existing values.

  • Pipe Operator: |> passes the result of the left side as the first argument to the right. Enables readable function chains: data |> parse() |> transform() |> save().

  • OTP GenServer: handle_call, handle_cast, handle_info. GenServer is a stateful process with a synchronous request/reply interface.

  • Supervision Trees: supervisors restart failed processes. Strategies: :one_for_one, :one_for_all, :rest_for_one. “Let it crash” philosophy.

  • Concurrency: processes are lightweight (not OS threads). Message passing with send/receive. Elixir processes are isolated — one crash doesn’t affect others.

  • Protocols and Behaviours: protocols provide polymorphism; behaviours define callback interfaces. Similar to type classes (Haskell) or traits (Rust).

Intuition

Elixir runs on the Erlang VM (BEAM), designed for building fault-tolerant, distributed systems. Everything is a function call — there are no loops, only recursion and higher-order functions like Enum.map. Pattern matching is pervasive: it’s used for function dispatch, error handling (case/with), and data destructuring. OTP provides battle-tested building blocks (GenServer, Supervisor) that implement the “let it crash” philosophy — processes fail independently and supervisors restart them. Elixir combines the robustness of Erlang with a modern, Ruby-like syntax.

Common Pitfalls

  • Pipe operator precedence: The |> pipe operator has low precedence — expressions in the pipe chain can bind unexpectedly. Use parentheses for complex arguments.
  • Agent vs GenServer: Using Agent for anything beyond simple state — Agent is a convenience wrapper; GenServer gives you full control over handle_call/handle_cast/handle_info.
  • Binary pattern matching: Forgetting that <<a, b::binary>> matches a byte and the rest as binary — b::binary is required to capture remaining bytes, not just b.
  • Tail recursion: Not all recursion is tail-recursive. Only the last call being the recursive call (with no further computation) allows the BEAM to optimise stack usage.
  • Erlang vs Elixir syntax: Elixir compiles to Erlang bytecode. Understanding Erlang documentation and error messages is essential for debugging.

Cross-References