Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages
Author's Final Manuscript
Open, type-level functions are a recent innovation in Haskell that move Haskell towards the expressiveness of dependent types, while retaining the look and feel of a practical programming language. This paper shows how to increase expressiveness still further, by adding closed type functions whose equations may overlap, and may have non-linear patterns over an open type universe. Although practically useful and simple to implement, these features go beyond conventional dependent type theory in some respects, and have a subtle metatheory.
Eisenberg, Richard A. et al. 2014. "Closed Type Families with Overlapping Equations." Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages, San Diego: 671-683.