FP has a reputation for being difficult to learn and understand because of its mathematical background. FP languages and design patterns are influenced by concepts that originated in many different mathematical fields. However, we can highlight category theory as one of the most significant fields of influence. We can think about category theory as an alternative to set theory, which defines the theory behind a series of data structures or objects known as algebraic data types.

There are many algebraic data types, and understanding all their properties and rules that they must implement requires a significant amount of time and effort. The following diagram illustrates the relationships between some of the most common algebraic data types:

The arrows in the diagram indicate that a given algebraic data type must implement the specification of some other algebraic...