Self-Learn Yourself Scala in 21 Blogs - #4

We are already using functional programming using Scala with the previous blog series of Self-Learn Yourself Scala in 21 Blogs (#1, #2, #3). Let's start with defining functional programming which is a programming paradigm that models computation as the evaluation of expressions and expressions are built using functions that don't have mutable state and side effects. But any guess how old is functional programming; you don't believe it's started around 1930 when the lambda calculus introduced. And now the lambda calculus is a formal mathematical system to investigate functions, function apps, and function recursion. At first glance it may seem odd to compare oop and functional programming at a pure versus impure level.