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diff --git a/src/pages/missionary.clj b/src/pages/missionary.clj new file mode 100644 index 0000000..2bb06de --- /dev/null +++ b/src/pages/missionary.clj @@ -0,0 +1,151 @@ +(ns pages.missionary + (:require [components :refer [page]] + [borkdude.html :refer [html]] + [highlight :refer [highlight-clj]])) + +(defn missionary [] + (page + (html + [:<> + [:h1 "FRP in Clojure with Missionary"] + [:h3 "August 2025"] + [:p "I've been working in Clojure on and off for nearly a decade now. In +that time, I've spent thousands of hours working in other languages +professionally: Python, Ruby, TypeScript / Flow / JavaScript, Kotlin, and Java. +I've experimented with many more, to varying degrees: Zig, Janet, Prolog, and +Factor, to name a few. At the end of the day, though, I always find myself +coming back to Clojure."] + [:p "Though it's hard to pin down exactly why I find myself so drawn by +the language, it seems to have something to do with the relatively high incidence +of exposure to new, mind-expanding ideas that I've experienced while working +in Clojure and its ecosystem."] + [:p "For one reason or another, Clojure seems to attract a high density of +smart people who are experimenting with fairly radical ways of solving hard +problems. Something about the combination of the language's simple macro system, +data orientation, reasonable performance, and practical approach to +functional programming make it a great foundation for building more complicated +experimental language constructs."] + [:p "It is via Clojure that I first came to be exposed to datalog, for example, +which helped me begin to be able to articulate why I struggled with SQL's +relativel lack of expressivity. From there, I discovered prolog and the world of +\"search programming\", which gave me an entirely different way to frame +certain problems."] + [:p "Similarly, I first learned of Datomic through Clojure, which blew my +mind the first time I encountered it. The idea of treating your entire database +as a single, immutable value would never have occurred to me on my own; +once I encountered it, however, the alternative seemed patently absurd."] + [:p "The Clojure library " [:span.inline-code "meander"] " showed me that term rewriting systems +could be used for data transformation. (Did you know that term rewriting systems +have the full power of turing machines?) The folks over at Hyperfiddle +have proven that you can effectively abstract away the network connection that +sits between a client and a server, and they have credited Clojure for that +accomplishment. Similarly, my experience so far with Rama, from Red Planet Labs, +have made it hard for me to go back to \"traditional backend programming\". +(I could write a whole series of posts on that topic. Reach out if you'd find +that interesting.) They, too, credit Clojure for their progress."] + [:p "In this post, I want to use the FRP library " [:span.inline-code "missionary"] " to give an +example of what it means to embed an entirely new concept within an existing +programming language. On the one hand, missionary is simply a library. On the +other hand, it differs significantly from the kind of library that you might +find in other programming languages because it introduces its own syntax and +semantics that integrate seamlessly with the host language, Clojure. (This is +the old \"promise of the DSL\" that lisps are famous for.)"] + [:p "First, though: what is missionary? At a high level, missionary +seeks to make it easier to write correct asynchronous (and concurrent) programs +correctly, efficently (meaning that it makes effective use of available CPU +resources), and in a manner that will feel comfortable to functional programmers. +To accomplish that, missionary draws inspiration from a number of interesting +programming ideas and diciplines:"] + [:ul + [:li "Functional Reactive Programming, or FRP"] + [:li "Process supervision"] + [:li "Structured concurrency"] + [:li "Ambiguous programming"] + [:li "TKTK"]] + [:p "To start our journey, I want to show you the equivelant of a \"hello, world!\" +program, written with missionary. This program captures the current time, in milliseconds; +it sleeps for one second; and then it captures the current time again."] + (highlight-clj + (require '[missionary.core :as m]) + + (def run + (m/ap (tap> [:a (System/currentTimeMillis)]) + (m/? (m/sleep 1000)) + (tap> [:b (System/currentTimeMillis)]))) + + (m/? (m/reduce {} nil run))) + [:p "(In these examples, you'll note my use of the " [:span.inline-code "(tap> ...)"] " function. This +function appends the value of its argument to a list. After the program runs, +I print the contents of that list to the \"tap contents:\" box below the code.)"] + + [:p "TKTK Note, however, that " [:span.inline-code "run"] " doesn't actually execute until we feed it +to the " [:span.inline-code "reduce"] " function. It's too early to explain how " [:span.inline-code "reduce"] " has anything +to do with running a program – we'll have to build some other intuition first. +For now, when you see " [:span.inline-code "reduce"] ", just think \"run a sequence of operations.\""] + + [:p "You might be thinking: " + [:em "I could write this code just as easily without missionary. +What's the point? "] + "Great question. We should go ahead and do that. Let's write this program once +without missionary, and then again with missionary but with a bit of additional +debugging thrown in:"] + + (highlight-clj + (defn log + "Emit `v` to `tap>`, capturing the current time and active thread along the way." + [v] + (tap> [v (System/currentTimeMillis) (.getName (Thread/currentThread))])) + (defn run-native [] + (log :native-a) + (Thread/sleep 1000) + (log :native-b)) + + (tap> (-> (run-native) + (time) + (with-out-str))) + + (def run-missionary + (m/ap (log :missionary-a) + (m/? (m/sleep 1000)) + (log :missionary-b))) + + (tap> (-> (m/reduce {} nil run-missionary) + (m/?) + (time) + (with-out-str)))) + ;; TODO: Fix bug where second log doesn't + ;; always print! + + [:p "A few things might jump out immediately."] + [:p "First, both " + [:span.inline-code "run-native"] " and " + [:span.inline-code "run-missionary"] + " block during their evaluation. Notice that the runtime + for each is approximately 1000ms."] + [:p "Second, " + [:span.inline-code "run-native"] + " evaluates the entire expression on the repl's main thread.i By contrast, " + [:span.inline-code "run-missionary"] + " seems to move the + form after the sleep expression to some kind of background thread. What's + that about?"] [:p "Oh, by the way. At the beginning of this post, I made + it clear that Clojure has had a major impact on the way I think about + programming, in large part because the language has facilities that make it + particularly attractive for experimentation. While I believe that to be + true, I know that Clojure is hardly alone in its expressiveness. If you are + a Haskeller, an OCameler, a Common Lisper, an APLer, or even a C + programmer, and you're thinking to yourself \"Clojure isn't special in this + regard\", well, I'm sure you're right! Shoot me an email with your + thoughts, I'd love to learn more about why your language of choice is + unique in this regard. I'll update this post with your contribution."] + [:h2 "References"] + [:ul + [:li "TODO flow spec"] + [:li "TODO task spec"] + [:li "TODO process supervision"] + [:li + [:a {:href "https://github.com/leonoel/missionary"} "Missionary"]] + [:li [:a {:href "https://github.com/hyperfiddle/electric"} "Electric Clojure"]] + [:li [:a {:href "https://github.com/noprompt/meander"} "Meander"]] + [:li [:a {:href "https://jimmyhmiller.com/meander-rewriting"} + "Introduction to Term Rewriting with Meander"]]]]))) |