Category Theory for the working Hacker 🐷

A category where a morphism is a relation between objects: the relation of being less than or equal. Let’s check if it indeed is a category. Do we have identity morphisms? Every object is less than or equal to itself: check! Do we have composition? If a <= b and b <= c then a <= c: check! Is composition associative? Check! A set with a relation like this is called a preorder, so a preorder is indeed a category.

Function is a morphism or called an ➡ There is a 🐈 egory that contains all sets called Set

Void is a set with nothing in it, no values

There's one with only one unit represented as ()

A preorder is a category where there is at most one morphism going from any object a to any object b