Thue (programming language)

Thue ( TOO-ay) is an esoteric programming language invented by John Colagioia in early 2000. It is a meta-language that can be used to define or recognize Type-0 languages from the 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 a semi-Thue grammar, named after the Norwegian mathematician Axel Thue. Colagioia describes the language 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."

Production rules

A Thue program starts with a rulebase, which is a series of substitution rules, each of this form:

lhs ::= rhs

The rulebase terminates with a lone production symbol on a line:

::=

The initial state is a series of symbols which follow the rulebase.

Thue consumes the initial symbols and substitutes the result of the rules for each of the initial state's symbols.

Thue terminates when lhs cannot be found in a resultant state.