Polymorphism in Elixir | Joseph Koski’s Blog

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.

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