👉 Containers, often referred to as higher-order containers or HOCs in some contexts, are a fundamental concept in functional programming, particularly in languages like Haskell and Scala. They extend the idea of function composition by allowing functions to take other functions as arguments or return functions as output, creating a hierarchy of abstraction. In this framework, a container is essentially a function that takes another function as its argument and returns a new function. This new function, when called, applies the original function to some input but encapsulates it in a higher-level abstraction, making complex operations more modular and reusable. For example, given a function `f` that takes an integer and returns its square, a container `c` might look like `c f = \text{map} f`, which applies `f` to every element in a list. This mechanism facilitates chaining operations and abstracts away low-level details, promoting cleaner and more maintainable code.
