Thue programming language

Thue is an esoteric programming language invented by John Colagioia in early 2000. It is a metalanguage that can be used to define or recognize Type-0 languages from Chomsky hierarchy. Because it is able to define languages of such complexity, it is also Turing-complete itself. Thue is based on a nondeterministic string rewriting system called semi-Thue grammar, which is named after (and possibly created by) the Norwegian mathematician Axel Thue. The author describes it as follows: "Thue represents one of the simplest possible ways to construe constraint-based programming. It is to the constraint-based paradigm what languages like OISC are to the imperative paradigm; in other words, it's a tar pit."