elixir

Elixir / Erlang: Idiomatic Efficiency Reference

When to Use

• Use this skill when the task matches this description: Language-specific super-code guidelines for elixir.

Table of Contents

1. [Pattern Matching & Guards](#patterns)
2. [Pipe Operator & Transforms](#pipes)
3. [Processes & OTP](#otp)
4. [Error Handling](#errors)
5. [Collections & Enum](#collections)
6. [Structs & Protocols](#structs)
7. [Anti-patterns specific to Elixir/Erlang](#antipatterns)

---

1. Pattern Matching & Guards {#patterns}

# ❌ Extracting with Map.get then checking
value = Map.get(map, :key)
if value != nil do
  process(value)
end

# ✅ — pattern match directly
case map do
  %{key: value} -> process(value)
  _ -> :noop
end
# or with if:
if value = map[:key], do: process(value)

# ❌ Nested case for multiple conditions
case fetch_user(id) do
  {:ok, user} ->
    case validate(user) do
      {:ok, valid_user} -> save(valid_user)
      {:error, reason} -> {:error, reason}
    end
  {:error, reason} -> {:error, reason}
end

# ✅ — with clause
with {:ok, user} <- fetch_user(id),
     {:ok, valid_user} <- validate(user) do
  save(valid_user)
end

# ❌ if/else for known shapes
def area(shape) do
  if shape.type == :circle do
    :math.pi() * shape.radius * shape.radius
  else
    shape.width * shape.height
  end
end

# ✅ — multi-clause function with pattern matc