https://blog.cofree.coffee functional programming, permaculture, math https://blog.cofree.coffee/2026-07-20-servant-auth-roles Mon, 20 Jul 2026 00:00:00 -0700 I wanted a nice way to create a roles system on top of servant-auth. This post walks through the design and implementation process. The end result is quite similar to OCharle's Who Authorized These Ghosts. You can see the final result here. https://blog.cofree.coffee/2025-03-05-chat-bots-revisited Wed, 05 Mar 2025 00:00:00 -0800 It has been a long while since my last post on chat bots; quite a bit longer then I intended to be honest. I would like to summarize here where the project has gotten as I think it has some cool ideas worth documenting. https://blog.cofree.coffee/2024-07-02-lensy-moore Tue, 02 Jul 2024 00:00:00 -0700 How far can we get leveraging the lens library in Haskell to model Moore Machines and Wiring Diagrams? https://blog.cofree.coffee/2024-03-03-lean-for-haskell-developers Sun, 03 Mar 2024 00:00:00 -0800 Last updated 2024-03-03 https://blog.cofree.coffee/2022-02-14-how-to-design-a-chat-bot Mon, 14 Feb 2022 00:00:00 -0800 I'm working on a library for designing highly composable protocol agnostic chat bots. The design is based on Mealy machines and heavily leverages Haskell's profunctor machinery. I want to walk through the early stages of the design process and how you might arrive at such an architecture. https://blog.cofree.coffee/2021-11-23-happy-and-alex-part-2-mvp Tue, 23 Nov 2021 00:00:00 -0800 In my last post I gave a brief introduction to Happy and parser generators. In this post I will continue the story with Happy's counterpart Alex. https://blog.cofree.coffee/2021-10-29-happy-and-alex-part-1-dont-worry-be-happy Fri, 29 Oct 2021 00:00:00 -0700 When I was first learning Haskell it was emphasized to me via blog posts, books, and conversations how wonderful Haskell is for language design. One of the major points in favor of this was parser combinators. https://blog.cofree.coffee/2021-08-16-how-free-monads-yield-extensible-effects Mon, 16 Aug 2021 00:00:00 -0700 The Free monad gives you a Monad for any Functor. The Free monad can also be used to construct extensible effect systems. I never understood why Free why this was the case. It turns out it is deeply connected to their ability to yield monads for functors. https://blog.cofree.coffee/2021-08-13-that-one-cool-reader-trick Fri, 13 Aug 2021 00:00:00 -0700 If you are writing an interpreter, odds are you will want to bind variables. If you are binding variables, there is a decent chance you will want to locally scope your variables. https://blog.cofree.coffee/2021-08-05-a-brief-intro-to-monad-transformers Thu, 05 Aug 2021 00:00:00 -0700 A few friends have recently asked about literature introducing Monad Transformers. The best introduction I have found was in Haskell Programming From First Principles. If you don't have, or want to purchase, this book, then here is a brief explanation with examples. https://blog.cofree.coffee/2020-12-22-finally-modular-arithmetic Tue, 22 Dec 2020 00:00:00 -0800 Fin _ is one of those data types that makes you take a step back and question how much you really understand typed functional programming. https://blog.cofree.coffee/2020-10-17-bounded-space-automata Sat, 17 Oct 2020 00:00:00 -0700 After reading Chris Penner's blog post on Conway's Game Of Life Using Representable and Comonads, I decided to implement a similar solution for the 1 dimensional automata Rule 110. Being such a simple algorithm I thought the implementation would be trivial. However, it turns out that working with arbitarily bounded spaces in the Store Comonad requires a clever use of dependent types to apply memoizaition as described in Chris' blog. https://blog.cofree.coffee/2020-10-16-hello-world Fri, 16 Oct 2020 00:00:00 -0700 Its October 2020, COVID-19 has wreaked havoc across the globe, the US is deeply divided along partisan lines, the environment is in collapse, the government is in a seemingly endless consitutional crisis, and I've decided to start blogging! What a time to be alive.