Coherence for Skew-Monoidal Categories
arXiv:1406.2064 · doi:10.4204/EPTCS.153.5
Abstract
I motivate a variation (due to K. Szlachányi) of monoidal categories called skew-monoidal categories where the unital and associativity laws are not required to be isomorphisms, only natural transformations. Coherence has to be formulated differently than in the well-known monoidal case. In my (to my knowledge new) version, it becomes a statement of uniqueness of normalizing rewrites. I present a proof of this coherence theorem and also formalize it fully in the dependently typed programming language Agda.
In Proceedings MSFP 2014, arXiv:1406.1534