Hacker News Reader

Category theory is all about adjoints. What's an adjoint? Adjoint and a norm give you the inverse.

Can you please elaborate.

Not sure what the poster had in mind, but I will refer you to some notes by a geophysicist about intuitively understanding adjoints:http://www.reproducibility.org/RSF/book/bei/conj/paper.pdf

This talks about adjoints of operators, which is where the category theory terminology comes from, but a pretty different concept overall