Design Patterns and Category Theory

The recent thread "From Design Patterns to Category Theory" (on Y Combinator's "Hacker News") comments on essays by Mark Seeman and includes some delightful bits by various contributors:

(cf Greatest Inventions (2011-06-09), Category Theory Concepts (2016-04-25), Ultimate Abstraction (2017-08-24), Put the Vast Storehouse in Order (2017-10-04), Category Theory is like a Lighthouse (2018-12-24), Why Care about Category Theory (2019-03-03), ...) - ^z - 2019-06-12