Polymorphism

Polymorphism classification

1. Ad-hoc polymorphism - Functions or operators behave differently based on argument types

• Function and method overloading - Multiple functions with same name, different signatures
  • CSharp example: 1-ad-hoc.cs
  • JavaScript emulation: 2-emulation.js
• Operator overloading - Custom behavior for built-in operators: 3-operator.cpp
• Type-class polymorphism - Ad-hoc polymorphism via type constraints (e.g. Haskell type classes, Rust traits)
• Coercion polymorphism - Implicit or explicit type conversions: 4-coercion.js

2. Subtype polymorphism - Objects of derived types can be used where base types are expected

• Class inheritance - IS-A relationship via base classes: 5-abstract.ts
• Interface / protocol polymorphism - Contracts that types must implement: 6-protocol.js
• Structural (duck typing) polymorphism - Compatibility based on structure, not explicit inheritance: 6-protocol.js

3. Parametric polymorphism - Code written generically to work with any type

• Generic functions - Functions parameterized by types: JS 9-generics.ts
• Generic data structures - Data structures parameterized by types: JS TS a-generics.js

4. Dispatch mechanisms - How the runtime selects which method to call

• Dynamic dispatch - Method chosen at runtime based on object type: 7-dynamic.js
• Virtual functions and methods - Base class methods overridable by derived classes: 8-virtual.cpp
• Multiple or multimethod dispatch - Method chosen based on multiple argument types