Functional programming has a reputation for being difficult to learn and understand due to its mathematical background. Functional programming languages and design patterns are influenced by concepts that originated in different mathematical fields. However, we can highlight category theory as one of the most significant influences. We can think about category theory as an alternative to set theory. It 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 the 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...