Most popular programming languages support functional programming. Kotlin is no exception. Most essential construct is an lambda expression. Lambdas are quite powerful. They simplify your code, make it more readable, they are new miracle that world have never seen before… But wait… Really?
Mathematicians know Lambda Calculus since 1930’s. First functional programming languages appeared before we went to Moon. Lisp exits since 1980’s. Nope. Most common programming languages have notion of either anonymous function or class, function references. Nothing new here.
