THE IDEAS OF CLOJURE

JCConf 2015/12/04

Randy Lien

Things I learn from Clojure

About me@randylien

UI Engineer

#WebAppsRocks

#JavaScriptIsNotSoJavaScript

#WhenIsNextReactJS.TwMeetup

#clojurians.tw@facebook

http://clojurians.tw

Survey!

Heard Clojure?

Clojure developer?

Enjoy Java development?

I dont know Java.

Speaker

History of programming languages

https://en.wikipedia.org/wiki/History_of_programming_languages

LISP

Clojure ?

React.js Conf 2015

Tapestry Dude - https://goo.gl/R5m3am (CC BY-SA 2.0)

The Creator of ClojureRich Hickey

https://goo.gl/R5m3am

"Hickey is the new Messiah of software development. Watch and listen to his talks, and you will understand."

http://bepsays.com/2014/07/08/how-rich-is-rich-hickey/

Few ideas I want to share

Philosophy

Philosophy

Focus

Simplicity

Empowerment

Pure functions

Expressive Practical

ClarityConsistency

Separation of

concernsConcise

Direct Interop

- The Joy of Clojure

Philosophy - Simplicity

Pure functions

Immutable

Simple abstractions

defprotocol

deftype

Philosophy - Focus

Syntax will not bother you

Consistency

Dynamic System

Almost everything defined in Clojure can be redefined (Even while program is running)

Use Macro you can build anything you want to do

Philosophy - Empowerment

Use Java Virtual Machine

Java is mature and has many libraries

JavaScript is everywhere (ClojureScript)

Consistency

Syntax does matter

Java + Python + JavaScript ?

JaPythonScript?

Data Types

Integers - 123

Doubles - 1.23

Ratios - 1/23

Strings - "JCConf"

"Double Quotes Only"

Characters - \J \C

Data Types (cont.)

Symbols - bar

Keywords - :foo

Booleans - true false

Null - nil

Regex - #"[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]+"

Data Structure Lists - (1 2 3)

Prepend

Vectors - [1 2 3]

Zero indexed. Append

Maps - {:a 1, :b 2, :c "3"}

Key-value pair

Comma will be ignored

Sets - #{1 2 3}

Unique. Unordered

function definition

function definition

doc string

Clojure

(+ 1 2)

(+ 1 2 3)

(into [] 2)

General

1 + 2

1 + 2 + 3

[].push(2)

Use host libraries - Java

Use host libraries - JavaScript

DEMO

functions & composition

functions & composition

map, reduce, filter

partial, comp

iterate

repeat, repeatedly

Many built-in functions and you dont need to create. Just compose it!

DEMO

Values

Values should be

Value!

operated by functions

time-relative

Immutable

Why Immutable?

Why mutable?

Why mutable?

Limitations of early computers: Small RAM and disk

New information replaces old

Why immutable?

No resource limitation

Persistent data structure

Record - Share the same data

Key to do functional programming

No side effect

atom is mutable

REPL Driven Development

REPL ?

ReadEvalPrint Loop

nREPL (network REPL)

Good for doing TDD

clojure.test

ClojureScript - Browser can connect to nREPL

REPL

DEMO - ClojureScript

REPL

DEMO - Clojure

Tooling Eco-system

Clojars

emacs

LightTable

Leiningen

Summary

Summary

Clojure is a practical functional programming language

Java and JavaScript are two major languages and Clojure and ClojureScript can run on them

Using REPL in your TDD practices would be helpful

Pure functions and Immutable data structure can make your system stable and easy to reason about

Summary (cont.)

Clojure has much better tooling and keep improving it

ClojureScript is hotter than Clojure!

Many companies are using Clojure

booking.com, Yahoo, Puppet, Walmart, twitter, heroku, nubanketc

STM, transducer, core.asyn

http://booking.com

If you want to know more

Living Clojure

The Joy of Clojure

ClojureScript Unraveled

Clojure Applied

Clojure for the Brave and True

Online resource

http://www.tryclj.com/

http://www.4clojure.com/

http://www.tryclj.com/http://www.4clojure.com/

Worth to watch

Simple Made Easy

Clojure Made Simple

The Value of Values

The Language of the System

http://www.infoq.com/presentations/Simple-Made-Easyhttps://www.youtube.com/watch?v=VSdnJDO-xdghttps://www.youtube.com/watch?v=-6BsiVyC1kMhttps://www.youtube.com/watch?v=ROor6_NGIWU

Thanks