Refal

Refal, short for Recursive Functions Algorithmic Language, is a functional programming language designed by Valentin Turchin and oriented toward symbolic computation such as string processing, language translation and artificial intelligence. It was first conceived in 1966 as a theoretical tool and saw its first working implementation in 1968, making it one of the oldest languages in the functional family. Turchin intended Refal to combine mathematical simplicity with enough practical power to write large, sophisticated programs. Unlike Lisp, its contemporary, Refal is built around pattern matching working together with term rewriting, so a Refal program is expressed as a set of rules that recognize patterns in data and rewrite them into new forms rather than as a sequence of explicit function calls. It uses strong, dynamic typing.