Introducing functional programming

During the 1930s, the mathematician Alonzo Church developed lambda calculus. This was the starting point for the functional programming paradigm, since it provided the theoretical grounds. The next step was the design of LISP (short for List Programming) in 1958, by John McCarthy. LISP is the first functional programming language, and some of its flavors, such as Common LISP, are still used today.

In functional programming (often abbreviated to FP), functions are first-class citizens; this means that software is built by composing functions, rather than objects, as OOP. This is done in a declarative way, Tell don't ask, by composing functions, promoting immutability, and avoiding the side effects and shared data. This leads to a more concise code that is resilient to changes, predictable, and easier to maintain and read by business people.

Functional code has a higher signal-to-noise ratio; we have to write less code to achieve the same thing as in OOP. By...