This is an old article (Sep 2011), but someone posted a link to it in IRC this morning, and I thought it would be of general interest to the group.
"Sometimes, the elegant implementation is a function. Not a method. Not
a class. Not a framework. Just a function. - John Carmack
Functional programming is an old idea with a distinguished
history. Lisp, a functional language inspired by Alonzo Church's
lambda calculus, was one of the first programming languages developed
at the dawn of the computing age. Statically typed functional
languages such as OCaml and Haskell are newer, but their roots go
deep—ML, from which they descend, dates back to work by Robin Milner
in the early '70s relating to the pioneering LCF (Logic for Computable
Functions) theorem prover.
... "