More ties than we thought

• Main Authors: Dan Hirsch, Ingemar Markström, Meredith L. Patterson, Anders Sandberg, Mikael Vejdemo-Johansson
• Format: Article
• Language: English
• Published: PeerJ Inc. 2015-05-01
• Series: PeerJ Computer Science
• Subjects: Necktie knots; Formal language; Automata; Chomsky hierarchy; Generating functions
• Online Access: https://peerj.com/articles/cs-2.pdf

We extend the existing enumeration of neck tie-knots to include tie-knots with a textured front, tied with the narrow end of a tie. These tie-knots have gained popularity in recent years, based on reconstructions of a costume detail from The Matrix Reloaded, and are explicitly ruled out in the enumeration by Fink & Mao (2000). We show that the relaxed tie-knot description language that comprehensively describes these extended tie-knot classes is context free. It has a regular sub-language that covers all the knots that originally inspired the work. From the full language, we enumerate 266,682 distinct tie-knots that seem tie-able with a normal neck-tie. Out of these 266,682, we also enumerate 24,882 tie-knots that belong to the regular sub-language.