typpiluokkia

Type classes are a programming language feature that enable ad-hoc polymorphism. They were first introduced in the Haskell programming language. Type classes provide a way to define a set of operations that can be implemented for different types. This allows functions to be written that work polymorphically over any type that implements a given type class.

Essentially, a type class acts as an interface or a contract. When a type is an instance of a type class, it promises to provide implementations for all the methods defined by that type class. For example, a `Show` type class might define a `show` function that converts a value into a string representation. Any type that wants to be printable would become an instance of `Show` and provide its own specific `show` implementation.

This mechanism allows for code reuse and abstraction. Functions can be written to operate on any type that supports certain operations without needing to know the specific underlying type. This is different from parametric polymorphism, where a function works on any type but does not constrain the operations that can be performed on it. Type classes introduce constraints, specifying that a type must support a particular set of operations to be used with a polymorphic function. The implementation of these operations can vary significantly between different types, leading to ad-hoc polymorphism.