Reading Category Theory for Programmers by Bartosz Milewski on stream.

Previous reading: 20260220035619

Part 1, Section 4:

• Composition of Logs
  • I feel like we just described what a Monad is.
• The Writer Category
  • This is section is just proving that the Writer Monad is composable.
• Writer in Haskell
  • Now we're doing the same thing in Haskell.
  • I remember that (>=>) is the Kleisli operator.
• Kleisli Categories
  • A Kleisli Category is a category based on a Monad.
  • A Kleisli Category has:
    • For objects, the types of the underlying programming language and morphisms from
    • For morphisms: functions that go from A to a type derived from B ("derived" is not referring to inheritance, just another type that takes B as a input) using an endofunctor in a category.
  • Monads allow us to give denotational semantics to programs without using side effects directly.

Challenge:
It appears that the challenge is to implement the Maybe monad, and I don't really want to do this right now.