Io
	And one quirky object system...
	That turned out to be useful...
	(blame ubuntu and freeglut for no full-screen)

Overview of Talk
	Who am I?
	Io's place in the world
	Differential Inheritance
	Questions

Who am I?
	name: Jonathan Wright
	irc: quag in #io on freenode
	email: quaggy@gmail.com
	web: www.quag.geek.nz

Number 2
	Year and a half
	Steve's Vision

Overview of Talk
	Who am I?
	***Io's place in the world***
	Differential Inheritance
	Questions

Buzz words
	OO
	Prototype based
	Message based
	Dynamic
	Actors
	Coroutines
	Futures
	Opengl
	Interpreted
	Macros

Other words
	Experiment
	Unification of concepts
	Small syntax
	Young
	Unstable

Purpose
	Gui framework
	Experiment
	Fun
	Dynamic
	4 years old, 6 years to go

Overview of Talk
	Who am I?
	Io's place in the world
	***Differential Inheritance***
	Questions

Differential Inheritance
	'Traditional' Objects (fast I promise)
	Meta Classes (fast I promise)
	Prototypes
	Differential Inheritance
	Benefits / Disadvantages
	Examples

'Traditional' Objects
	C++, and friends
	Classes
	Objects
	Inheritance

Dynamic Classes
	Ruby, Python, Smalltalk, CLOS, and friends
	Classes become Objects
	Classes have classes
	Changing an Object's class on the fly
	Generating classes
	Meta Classes
	...

Prototypes
	Unify
	Copying
	Add more stuff
	Simplifies
	More dynamic
	Harder to optimise

Differential Inheritance
	Delegating
	Add more stuff
	A is like B except for <differences>

Examples
	Elephants
	OHPs

Not New
	AI, Frames, Slots, Elephants
	Newton Script

What can they do?
	Factoring!
	Behaviour
	Data

What can they do?
	Classes
	Multiple Inheritance
	Mix-ins
	Classic Prototypes
	Scopes
	Namespaces
	Dynamic type (State pattern)

What do we gain?
	Object System which is:
	Simple
	Flexible
	Dynamic
	'multi-paradigm'

What do we lose?
	The usual suspects:
	Speed
	Memory usage

Example Time!
	elephant := {legs = 4, trunk = 1, ears = "large", size="massive"}
	Non-standard syntax
	elephant := Object clone do(legs := 4; trunk := 1; ears := "large"; size := "massive")

Code to do it...
	Object curlyBrackets := method(
	    result := Object clone
	    call message arguments foreach(i, arg,
	        if (arg name == "updateSlot" or arg name == "setSlot" or arg name == "setSlotWithType",
	            result newSlot(arg argAt(0) cachedResult, call sender doMessage(arg argAt(1), call sender))
	        ,
	            result newSlot(arg name)
	        )
	    )
	    result
	)

Dumbo is like elephant
	zooElephantSeenAsKid := {legs = 4, tusks = 2, size="massive"}
	dumbo := zooElephantSeenAsKid clone

Dumbo has more data
	elephant := {legs = 4, eyes = 2, ears = "large", nose = "trunk"}
	dumbo := elephant clone
	dumbo name := "Dumbo"
	dumbo jacket := "red"

Dumbo overrides existing data
	elephant := {legs = 4, tusks = 2, size = "massive"}
	dumbo := elephant clone
	dumbo tusks = 1
	dumbo size = "smallish"

Learn more about elephants
	elephant := {legs = 4, tusks = 2, size = "massive"}
	dumbo := elephant clone
	elephant seesMouse := method(freakout; runAway; cry)
	elephant tail := 1

Case Study: Java App Configuration
	Java tool to test an 'Integration Engine'
	Configurable message processing & manipulation server
	Receives, 'processes' and sends messages
	Graphical programming
	Can communicate using: tcp, ssl, directories, database, jms,
	   http, soap, serial, ftp, smtp...

Test Plan
	1. Send message
	2. Receive message
	3. Check received message
	4. Record results
	5. Repeat

Configuration per test message
	name or id
	Interface to send with (protocol, ports, hosts, paths...)
	success / failure
	test message file
	expected message files
	for each expected message file:
		comparison technique
		receive interface
		

Configuration Summary
	Lots of information needed per message
	1000s messages -> duplication

Solution
	Lexically scoped
	Named interfaces & comparators

Example
	test "edi to three xml"
		send using tcp, localhost, 8889
		receive using tcp, localhost, 9998
		message file "a.edi"
			expect file "x.xml"
			expect file "y.xml"
			expect file "z.xml"
		comparator xml
		failing "Tim broke it last night"

Example
	message file "a.edi"
		expect file "x.xml"
			comparator xml
			succeeding
		expect file "b.edi"
			comparator edi
			failing

Example
	group
		send using tcp, localhost, 8889
		failing "not implemented functionality yet"
		test
		test
	group
		send using directory "/var/spool/msgs"
		succeeding "implemented last night"
		test
		test

Experience
	Differential inheritance objects useful

Questions
	http://iolanguage.com
	http://www.quag.geek.nz (The www is needed)
	#io on freenode
	Jonathan Wright <quaggy@gmail.com>