applying the paradigms of core.async in clojure and clojurescript
TRANSCRIPT
Paradigms of core.async
LambdaJam Brisbane Workshop May 2014 Julian Gamble @juliansgamble
!
Github repo http://bit.ly/ylj14-‐clojure
Paradigms of core.async
LambdaJam Brisbane Workshop May 2014 Julian Gamble @juliansgamble
!
Github repo http://bit.ly/ylj14-‐clojure
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)
BenefitsIn 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
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
Requirements
• Prerequisites are high! (No intro-to-lang classes)
• Text editor
• Leiningen installed
• Internet connection preferable but not essential (Cloning github repo)
functional programming in Australia
functional programming in Australia
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)
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
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
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
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
2-basic-example• Open the PDF and then the code
-‐main function
first go block
second go blockmy-‐q>! <!
2-basic-example
2-basic-example
3-basic-multi-chan-example-‐main function
first go block
third go block
my-‐q1>!
alts!
second go block my-‐q2>!
3-basic-multi-chan-example
4-tim-baldridge-10K-processes
make-‐scene function
make-‐cell function10K
go block 1. Set colour 2. Paint canvas cell 3. Pause for random interval 4. Loop
5-not-10K-processes
makeScene function10K
makeCell function
mainLoop function
100
6-swanodette-10K-processes
let block render-‐loop render!‘render’ ‘queue’
[idx v] [idx v]
core.async channel parameter passed in during function call
7-rich-hickey-original-ants-demo-‐main function
animation agent
ant behaviour agent
evaporation agent
world symbol (vector of vectors)
send-‐off send-‐offsend-‐off
8-ants-cljs-no-asyncanimate function
send-‐off-‐animation function
behave-‐ants function
evaporate function
world symbol (vector of vectors)
single call single callsingle call
requestAnimationFrame (callback)
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
Questions?
LambdaJam Brisbane Workshop May 2014 Julian Gamble @juliansgamble
!
Github repo http://bit.ly/ylj14-‐clojure [Then the final slide]
