Classes Are Premature Optimization

Justin Lovehttp://www.delicious.com/rauros/prototypal

http://www.delicious.com/rauros/oop (recent)http://spkr8.com/t/4808

Justin Loveslides@JustinLove.name

http://JustinLove.name

@wondible

Outline

• OOP

• Classical

• Prototypal

• Performance

• What can we do better?

• Review

class ____ { ...}

object ____ { ...}

Class Oriented?

class ____ { ...}

OOP-or-

COP?

OOP

Those who do not remember history are condemned to repeat it.

George Santayana

(Chances are I’m repeating it right now.)

Alan Kay

EncapsulationLocal

RetentionProtection

Hidingof State-process

Genericity

Commonly, PolymophisimAlan Kay spoke of Algebras

Extreme late binding

Messaging

Object decides how to react.

Self Contained Tapes

OOP

EncapsulationGenericityMessaging

Classes

Inheritance

“Five words

objectmessageclassinstancemethod

make up the vocabulary with which Smalltalk

is discussed.”

Smalltalk-80, The Language, p.51

Smalltalk 71727680

Classes

Inheritance

Metaclasses

Alan Kay2003

“So I decided to leave out inheritance as a built-in feature until I understood it better.”

Alan Kay2003

“[...] backslid towards Simula and did not replace the extension mechanisms with safer ones that were anywhere near as useful.”

Classical

Sketchpad

1963

Generalvs.

Specific

Simula-67

C++Javaetc.

Classes Instances

Segregation

Plato

Formvs.

Matter

Descriptionvs.

Representation

Metaclass

“Class of classes”

RubyRuby Logo © 2006, Yukihiro Matsumoto

I’m not smart enough for Ruby’s

object system.

Peter DeutschThe Past, Present, and Future of Smalltalk

1989

“metaclasses have proven confusing to many users, and perhaps in the balance more confusing than valuable.”

Accidental Complexity

William of Ockham

“entia non sunt multiplicanda praeter necessitatem”

William of Ockham

“entities must not be multiplied beyond necessity”

Prototypal

Henry LiebermanOOPSLA 1986

http://web.media.mit.edu/~lieber/Lieberary/OOP/Delegation/Delegation.html

Using Prototypical Objects to Implement Shared Behavior in Object Oriented Systems

Self

1987

Abstractions

Objects

(Classes)

Objects

Abstractions?

one

one = object.clone

one two

two = one.clone

P

one two three .....

one = proto.clonetwo = proto.clone

three = proto.clone

YouAin’tGonnaNeed It

Singleton

Singleton (in JS)

var singleton = { ...};

Ex-Nihilo

“Out of Nothing”

Singleton: Self

clone = (self)

Prototypal Singleton

singleton.clone = function() { return this;};

Hard-core Singleton

function Singleton() { return Singleton.prototype;}

Near Miss

Near Miss

Near MissDay

Kin

Near Miss

var kin = day.clone("Kin");

Near Miss

clone: function(name) { var o = Object.create(this); o.name = name; ... return o;},

Near Miss

... // independent existence. o.scale = 0; o.position = 0; o.time = 0; ...

Object.create()

• ES5

• Firefox 4

• Safari 5

• Chrome 5+

• http://kangax.github.com/es5-compat-table/

Object.create()

Object.create = function(o) { function F() {}; F.prototype = (o || {}); return new F();}

http://javascript.crockford.com/prototypal.html

But Wait!

Object

Foo

obj

def obj.bounce “whee!”end

Ruby

Object

Foo

<***> obj

def obj.bounce “whee!”end

Object

Foo

<***> obj

def obj.bounce “whee!”end

obj.class

Object

Foo

<***> obj

def obj.bounce “whee!”end

lookup chain

Object

Foo

<***> obj

def obj.bounce “whee!”end

AccidentalComplexity

Nested Context

Nested Context

Like {block scope}.

(Or function scope in Javascript.)

Nested Context

under: function(path, f) { var m = Object.create(this); m.cd(path); f(m);},

Performance

Structured Memory

Programming as Experience:The Inspiration for Self

1995

Self runs

“2.3 times slower than optimized C++.”

Self includes: SmalltalkMario Wolczko

“all [sample] Smalltalk programs run faster in the the Self system, some significantly more so.”

Omega

1990Statically-typed prototypes

Design-Timevs.

Run-Time

Kevo

1993Concatative

‘Clone families’

Lisaac

2003Compiled.

44% slower to 17% fasterthan c.

http://www.lisaac.org/documentation/benchmarks

Duck TypesNot

Responsibility

V8 Logo © 2006 Google

V82008

V8 Logo © 2006 Google

Generated Code

V8 Logo © 2006 Google

Hidden Classes

Javascript

1996

Javascript

Is not an Object-Oriented Programming Language

Genericity

PASS

Messaging

FAIL*Partial support in ES5 and Harmony

Encapsulation

FAIL*Work-around with closure.

Peter DeutschThe Past, Present, and Future of Smalltalk

1989

“inheriting implementation [...] tends to create difficulties in subsequent evolution and often reflects insufficient understanding.”

Copyvs.

Delegation

Shared Data

Shared Data

Shared Data

Shared Data

......

...

...

......

Seph

Stateless Delgation

http://olabini.com/blog/2010/07/preannouncing-seph/

Sparse Objects

Sparse Objects

Sparse Objects

new Disk('Minute', unit.MS_S, 1, T("seconds/minute"), { colors: '#d22'})

Sparse Objectsnew Disk('Solar Year', unit.MS_D, T("days/~month"), 12, { colors: ['blue', 'green', 'orange', 'brown'], ...

Sparse Objects

... majorNames: ['~January'...], subDivide: 4, major: 3*4, median: 1*4, ...

Sparse Objects

... render: function(context) { context.save(); context.rotate( 6.28 * -9 / 365); ...

Flyweight

Flyweight

Flyweight

Flyweight

Flyweight

item: function(d) { var i = Object.create(this); i.dot = d; return i;},

Shared Behavior

Shared Behavior

Shared Behavior

Shared Behaviormint: function( head, pattern, action) { var my = this.dup(); my.head = head; my.pattern = pattern; my.action = action; return my;},

Shared Behavior

dup: function() { return Object.create(this);},

*

*

*

Prototype

Instances

Do I use class patterns?

YES

Do I use class patterns

for everything?

NO

a

Objects

Classes

a

Self

Smalltalk

Classesare aUsefulPattern

But notthe onlyPattern

Use Classes

Because You Want To

Use Classes

Because You Have To

Not

Language Designers

Considerprototypal

Monoculture

Language Designers

Don’t(blindly)

EmulateJavascript

What Might we Do Better?

Multiple Inheritance

Multiple InheritanceDelegates

Multiple Del.: Self

parent* = defaultBehaviorclonable* = Traits clonable

IO

2003

http://iolanguage.com/

Io is a prototype-based programming language inspired by Smalltalk (all values are objects, all messages are dynamic), Self (prototype-based), NewtonScript (differential inheritance), Act1 (actors and futures for concurrency), LISP (code is a runtime inspectable/modifiable tree) and Lua (small, embeddable).

Multiple Del.: IO

obj appendProto(Foo)obj prependProto(Bar)

Alan Kay

“But no comprehensive and clean multiple inheritance scheme appeared that was compelling enough to surmount Dan's original Simula-like design.”

Super

The Stripetalk Papers (1989), referencing

The Learnability of Object-Oriented Programming Systems (1986)

“this construct is known to be confusing to novices.”

Kevo

1993Concatative

‘Clone families’

Constraint Systems

Review

History

OOP

Classical

Prototypal

Performance

We’re Stuck with

Javascript

Learn How to Use It

Prototype

Instances

Shared Behavior

Shared Data

Singleton

Flyweight

Nested Context

Justin Loveslides@JustinLove.name

http://JustinLove.name

@wondible

http://www.delicious.com/rauros/prototypalhttp://www.delicious.com/rauros/oop (recent)

http://spkr8.com/t/4808