Languages / Concept
Lambda Calculus
Computation from nothing but functions.
In 1936 Alonzo Church introduced the lambda calculus: a formal system with only three things — variables, function abstraction (written λx.E), and application. That is the entire language, and yet it is Turing-complete. It can express any computation at all.
It is one of the two great answers to “what is computation?” (Turing machines are the other), and it is the theoretical root of functional programming. Lisp took its ideas into a practical language in 1958, and through Lisp they reach Clojure.
Sources
- Stanford Encyclopedia of Philosophy, “The Lambda Calculus” — a careful, readable introduction to Church’s system.
See also: Lisp.