Applying the paradigms of core.async in Clojure and ClojureScript
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In this workshop you’ll see a Clojure program that visually demonstrates Clojure’s concurrency semantics and then see how to solve the same underlying concurrency problems using core.async. You’ll see the mapping between programming paradigms you already know and core.async concepts. You’ll apply this in the browser with ClojureScript.
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Applying the paradigms of core.async in Clojure and ClojureScript
- 1. Paradigms of core.async LambdaJam Brisbane Workshop May 2014 Julian Gamble @juliansgamble ! Github repo http://bit.ly/ylj14-‐clojure
- 2. Paradigms of core.async LambdaJam Brisbane Workshop May 2014 Julian Gamble @juliansgamble ! Github repo http://bit.ly/ylj14-‐clojure
- 3. Getting set up • Clone the repository at: • http://github.com/juliangamble/lambdajam-2014- core.async-workshop or http://bit.ly/ylj14-clojure • Or get a copy of the repository and the maven libraries from a usb (or sharing on my computer)
- 4. Benefits In this workshop you will gain an understanding of: • go blocks and how they do concurrency • core.async queues • go block timers • alts! functions and how it enables reading multiple queues • how core.async processes work in ClojureScript • the visual impacts of how the core.async function enables simple ‘process-level’ pauses • how to use core.async to separate out the calculation and display parts of your code
- 5. Benefits In this workshop you will gain an understanding of: • how to use core.async to send a queue of updates to the display layer • the original ants implementation Rich Hickey used to demonstrate concurrency features in Clojure • converting a Clojure code-base to ClojureScript • using shared data structures in ClojureScript • a working knowledge of converting a single-threaded ClojureScript application to a concurrent one using core.async
- 6. Requirements • Prerequisites are high! (No intro-to-lang classes) • Text editor • Leiningen installed • Internet connection preferable but not essential (Cloning github repo)
- 7. functional programming in Australia
- 8. functional programming in Australia
- 9. Overview • We have 7 items to work through: Item Description 1-‐references API Reference material 2-‐basic-‐example core.async Hello World 3-‐basic-‐multi-‐chan-‐example Handling multiple channels 4-‐tim-‐baldridge-‐10K-‐processes Using core.async in ClojureScript 5-‐not-‐10K-‐processes Trying to mimic core.async in raw js 6-‐swanodette-‐10K-‐processes Using core.async for an animation pipeline in js 7-‐rich-‐hickey-‐original-‐ants-‐demo The Swing demo Rich Hickey used to demo Clojure concurrency 8-‐ants-‐cljs-‐no-‐async The actual workshop (don’t look at solution unless you really need it)
- 10. How do the exercises work? Inside each of the 7 directories is a PDF with the following headings: • Code to Read • Things to Note In the Code • Code Model • Activities • Questions for Reflection
- 11. What is core.async? • A set of primitives for creating, reading and writing to queues • A code walking macro that splices go blocks into state machines • A mechanism for asynchronous computation • A library in both Clojure and Clojurescript
- 12. Why does it relate to functional programming? • Clojure is a functional language • Clojure’s immutable data structures are based on Okasaki’s book – Purely Functional Data Structures • We’ll be comparing different methods of solving concurrency problems in a functional language (STM vs CSP) • core.async is implemented using a sophisticated Lisp macro - something only possible in a functional language • in non-functional languages like Go and C# - CSP is achieved by compiler-extensions - whereas in a functional language like Clojure - this functionality comes as a mere library
- 13. What is CSP? • Communicating Sequential Processes • Comes out of process calculi – an attempt in the 1970’s [Transputer era] to optimise computer usage through specialised algebra. • Based on message passing via channels • Subject of 1978 Book by C.A.R. Hoare
- 14. 2-basic-example • Open the PDF and then the code -‐main function first go block second go >! my-‐q block <!
- 15. 2-basic-example
- 16. 2-basic-example
- 17. 3-basic-multi-chan-example -‐main function first go block third go block >! my-‐q1 alts! second go block my-‐q2 >!
- 20. 4-tim-baldridge-10K-processes make-‐scene function make-‐cell function 10K go block 1. Set colour 2. Paint canvas cell 3. Pause for random interval 4. Loop
- 23. 5-not-10K-processes makeScene function 10K makeCell function mainLoop function 100
- 26. 6-swanodette-10K-processes [idx v] [idx v] let block ‘render’ render-‐loop ‘queue’ render! core.async channel parameter passed in during function call
- 29. 7-rich-hickey-original-ants-demo -‐main function send-‐off send-‐off send-‐off animation agent ant behaviour agent evaporation agent world symbol (vector of vectors)
- 35. 8-ants-cljs-no-async animate function requestAnimationFrame single call single call single send-‐off-‐ animation function behave-‐ants function (callback) evaporate function world symbol (vector of vectors) call
- 38. Workshop Activity • Make the changes described in pdf #8 to change this to a core.async ClojureScript program • Then work through the challenges in the ‘Questions for Reflection’ question
- 39. Questions? LambdaJam Brisbane Workshop May 2014 Julian Gamble @juliansgamble ! Github repo http://bit.ly/ylj14-‐clojure [Then the final slide]