Clojure_ Functional Con Currency for the JVM Presentation

8/2/2019 Clojure_ Functional Con Currency for the JVM Presentation

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2009 Formos Software Development


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http://xkcd.com/297/


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Code is Data


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ReadEvalPrintLoop


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Operating System

JVM

Java Libraries

User Classes

ClojureRepl Input

ClojureSource Files

JavaCompiler

Source Code

Evaluator


There IsNo Interpreter


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Clojure Literals


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Clojure Literals


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Java Interop


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Java Interop


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1

2

3

lst


Clojure Collections: Lists

4


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Clojure Collections: Vectors


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Clojure Collections: Map


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Clojure Collections: Sets


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Paul Graham


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Functional Programming in Java


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Functional Java Collections


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Functional Clojure Collections


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First Class Functions


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y

z

col

x


Life without the for loop

#


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Life without the for loop

f

f

f


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for: list comprehension


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Java: Data Encapsulated in Objects

Person

firstName: "Howard"lastName: "Lewis Ship"

age: 42

Person

firstName: "Scott"lastName: "Simon"

age: 44

Person

firstName: "Molly"lastName: "Newman"

age: 29

Person

firstName: "David"lastName: "Goldman"

age: 42


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Clojure: Data in Transformable Collections

{ }:first-name Howard

:last-name Lewis Ship

:age 42

{ }:first-name Scott

:last-name Simon

:age 44

{ }:first-name Molly

:last-name Newman

:age 29


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Paul Graham


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Clojure: Software Transactional Memory

500.

2500.

6700.

2800.

- 500. + 500. - 300. + 300.

500.

2800.

6700.


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Retries: Transactions Are Speculative

500.

2300.

- 500.

2500.

+ 500.

6700.

- 300.

+ 300.

500.

2800.

6700.6700.

2800.

- 300. + 300.

X

2500.


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Managing Mutation

What can change?

Reference types: atom, var, agent, ref

When can they change?

When are changes visible to other threads?


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Atoms

Shared, Global

Changes are atomic, synchronous, &non-blocking

(swap!): Pass value to function yielding new value

(reset!): Force new value, regardless of existing value


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Vars Per-Thread Mutables

(def) sets global binding

(binding) to set up a per-thread override

(set!) if per-thread binding


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Interfacing with Java APIs


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Function

Value

...

Namespace Var


Everything's a Var!


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Functions are stored in Vars


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Agents Single Thread Writes


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Refs Software Transactional Memory


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Concurrency Notes

All reference types can have a validator

function

All refs can have a watcher: an agent notified

of changes

(send) inside (dosync) waits until successfulcompletion

No guarantees when calling Java objects


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Jon Bentley and Doug McIlroy


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Clojure

1.0 release: May 4 2009

Simple, regular syntax

Improves on Lisp: vectors, maps, sets

Fully integrates with Java

Impressive functional & concurrency support

Manyfeatures not covered here


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F S f D l

2007 Jon Fife

http://flickr.com/photos/good-karma/577632972/

2008 Marcin Wichary

http://flickr.com/photos/mwichary/2222776430/

2007 James Manners

http://flickr.com/photos/jmanners/443421045/

2008 Daniel Chanhttp://flickr.com/photos/chanchan222/2847443980/

2005 Jack Keene

http://www.flickr.com/photos/whatknot/3118124/

A. Lipson 2003

http://www.andrewlipson.com/escher/relativity.html

2007 Alan Chia

http://flickr.com/photos/seven13avenue/2080281038/

2007 Woodley Wonderworks

http://flickr.com/photos/wwworks/2222523486/

Clojure_ Functional Con Currency for the JVM Presentation

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