Elixir Conventions

Control Flow

• •Prefer with chains over nested case.
• •Use Enum.reduce_while or Enum.flat_map over Enum.reduce with internal conditionals.
• •Pattern match in function heads rather than branching in the body.

Types & Structs

• •Use typedstruct for struct definitions.
• •Startup arguments use a startup_options union type:
  elixir

  @type startup_options ::
          {:node_id, String.t()}
          | {:id, atom()}
  
  @spec start_link(list(startup_options())) :: GenServer.on_start()
  

• •Keep type definitions near the top, after use/alias blocks.

GenServer / CQRS

• •call for reads or synchronization only. Writes use cast.
• •handle_call body: {:reply, do_foo(...), state} — core logic in the do_ function.
• •Never call a callback from another callback.
• •Actor modules require three sections:
  elixir

  ############################################################
  #                      Public RPC API                      #
  ############################################################
  
  ############################################################
  #                    GenServer Behavior                    #
  ############################################################
  
  ############################################################
  #                  GenServer Implementation                #
  ############################################################
  

Documentation

• •First-person voice: "I am the X module." / "I return the Y."
• •@moduledoc starts with one-sentence purpose.
• •### Public API section listing all public functions.
• •All public functions need @doc and @spec.

Examples

• •Live in lib/examples/e_<module>.ex.
• •Module name pattern: E<Module> (e.g., ENode, EShard).
• •Use import ExUnit.Assertions for assert.

Interactive Testing

• •Run one-off expressions: timeout 60 mix run -e 'code' (never use --no-halt, it hangs the VM).
• •Inspect process state: :sys.get_state(pid)
• •Query Mnesia:
  elixir

  :mnesia.transaction(fn -> :mnesia.match_object({table, :_, :_}) end)
  

Formatting

• •78 character line length.
• •Run mix format before finalizing.
• •Section headers use banner comments:
  elixir

  ############################################################
  #                      Section Name                        #
  ############################################################