Functional Programming Core Concepts

Functional Programming is an approach to building software from pure representations of rules. The functions-as-rules-based approach has its ancestry rooted in the Lambda Calculus, the first real Functional Programming syntax whose notation shapes the fundamental aspects of the paradigm. Any attempt at writing pure functions in PHP, irrespective of whether they are named functions, closures, or methods, involves creating relevant parameterized expressions—a practice that characterizes the Lambda Calculus. This chapter shifts attention away from the introductory material in the previous chapter to an exploration of the artifact at the epicenter of Functional Programming—the function.