Thue

Description #

Thue is an esoteric, non-deterministic programming language based entirely on semi-Thue string rewriting systems. It treats computation as a series of rule-based string replacements, with no variables, loops, or flow control—just grammar rewriting.

History #

Thue was created by John Colagioia in 2000. It’s named after mathematician Axel Thue, whose early 20th-century work on formal languages laid the foundation for string rewriting systems. The language is powerful yet minimal, designed to challenge traditional programming paradigms.

Hello World Code #

a::=~Hello, World!
::=
a

This program rewrites a into Hello, World!, then terminates.

How to Run #

Option 1: Online

• Try It Online – Thue

Option 2: Local

Save program in a .thue file

Use an interpreter such as Thue.py

Run:

python thue.py hello.thue

Key Concepts #

• Rule-based rewriting
• No functions, loops, or variables
• Uses pattern matching with ::=
• Non-deterministic if multiple rules match
• Minimal yet Turing complete
• Strings are both code and data
• Suitable for symbolic manipulation
• Can simulate any other esolang
• Logic flows through rewriting, not execution
• Great for theoretical exploration of computation

Try It Online #

• TIO – Thue

Fun Facts #

• The shortest Turing-complete language by syntax
• Can simulate complex logic using just string rewriting
• One of the few languages where grammar = logic

Resources #

• Thue on Esolangs
• TIO Runner – Thue
• Thue Interpreter (Python)