Which simple types have a unique inhabitant? (English) Zbl 1360.68341
Proceedings of the 20th ACM SIGPLAN international conference on functional programming, ICFP ’15, Vancouver, Canada, September 1–3, 2015. New York, NY: Association for Computing Machinery (ACM) (ISBN 978-1-4503-3669-7). 243-255 (2015).