QFM086: Elixir Reading List - October 2025

Elixir protocols provide polymorphic behavior by dispatching function calls based on the runtime type of the first argument, allowing different implementations for different data types without inheritance. Unlike object-oriented interfaces, Elixir protocols can include a fallback implementation using @fallback_to_any true and defimpl Speak, for: Any, providing safe defaults when no specific type implementation exists. However, protocols have a key limitation: they dispatch only on the first argument, so heterogeneous comparisons (like comparing a Cat to a Duck) require relaxed pattern matching to avoid crashes.

Elixir is implementing set-theoretic types into its compiler, featuring a gradual type system that remains sound while allowing dynamic() types that preserve partial type information rather than discarding it entirely. The type system uses set operations (unions, intersections, negations) for composition and currently focuses on inferring types from existing programs to detect bugs without requiring code modifications, with user-provided type signatures planned for future releases.