1. Stéphane Ducasse 1
Stéphane Ducasse
stephane.ducasse@inria.fr
http://stephane.ducasse.free.fr/
A Little Journey in the
Smalltalk Model

2. S.Ducasse 2
A pure and minimal object model
Less is more!

3. S.Ducasse 3
No constructors
No types declaration
No interfaces
No packages/private/protected
No parametrized types
No boxing/unboxing
Still powerful

4. S.Ducasse 4
1600 simultaneous
users
1.9 billions objects
10 000 updates/day
QuickTime™ and a
BMP decompressor
are needed to see this picture.
QuickTime™ and a
BMP decompressor
are needed to see this picture.

5. S.Ducasse 5
QuickTime™ and a
BMP decompressor
are needed to see this picture.
QuickTime™ and a
BMP decompressor
are needed to see this picture.
QuickTime™ and a
BMP decompressor
are needed to see this picture.
QuickTime™ and a
BMP decompressor
are needed to see this picture.
QuickTime™ and a
BMP decompressor
are needed to see this picture.

6. S.Ducasse 6
Objects are instances of Classes

7. S.Ducasse 7
Objects are instances of Classes
(10@200)

8. S.Ducasse 8
Objects are instances of Classes
(10@200) class

9. S.Ducasse 9
Objects are instances of Classes
(10@200) class
Point

10. S.Ducasse 10
Classes are objects too

11. S.Ducasse 11
Classes are objects too
Point selectors

12. S.Ducasse 12
Classes are objects too
Point selectors
> an IdentitySet(#eightNeighbors #+ #isZero #sortsBefore: #degrees #printOn: #sideOf: #fourNeighbors #hash
#roundUpTo: #min: #min:max: #max #adaptToCollection:andSend: #quadrantOf: #crossProduct: #=
#nearestPointOnLineFrom:to: #bitShiftPoint: #* #guarded #insideTriangle:with:with: #grid: #truncateTo: #y #setR:degrees:
#normal #directionToLineFrom:to: #truncated #nearestPointAlongLineFrom:to: #theta #scaleTo: #encodePostscriptOn:
#> #asPoint #extent: #r #roundTo: #max: #interpolateTo:at: #triangleArea:with: #angleWith: #dotProduct:
#isSelfEvaluating #'<=' #to:intersects:to: #'//' #isInsideCircle:with:with: #< #scaleFrom:to: #corner: #to:sideOf: #x #'>='
#roundDownTo: #onLineFrom:to:within: #transposed #ceiling #angle #basicType #translateBy: #asFloatPoint #''
#adaptToNumber:andSend: #abs #negated #octantOf: #asIntegerPoint #flipBy:centerAt: #scaleBy: #floor #onLineFrom:to:
#isPoint #reflectedAbout: #/ #dist: #asNonFractionalPoint #bearingToPoint: #reciprocal #rotateBy:centerAt:
#rotateBy:about: #rounded #setX:setY: #squaredDistanceTo: #normalized #veryDeepCopyWith: #- #storeOn: #rect:
#deepCopy #isIntegerPoint #min #adhereTo: #adaptToString:andSend:)

13. S.Ducasse 13
Classes are objects too
Point instVarNames

14. S.Ducasse 14
Classes are objects too
Point instVarNames
>#('x' 'y')

15. S.Ducasse 15
Methods are public

16. S.Ducasse 16
Instance variables are protected

17. S.Ducasse 17
Single Inheritance

18. S.Ducasse 18
Single Inheritance
Object subclass: #Point
instanceVariableNames: 'x y'
classVariableNames: ''
poolDictionaries: ''
category: 'Graphics-Primitives'

19. S.Ducasse 19
1
2

20. S.Ducasse 20
Classes are objects too

21. S.Ducasse 21
Classes are objects too
Point class

22. S.Ducasse 22
Classes are objects too
Point class
>Point class

23. S.Ducasse 23
Classes are objects too
Point class
>Point class
“Point class” is an anonymous class with only one
instance: Point

24. S.Ducasse 24
Class Parallel Inheritance

25. S.Ducasse 25
Lookup and Class Methods
1
2
1
2
Workstation withName: ‘BigMac’
aWorkstation
name

26. S.Ducasse 26
About the Buttons

27. S.Ducasse 27
Summary
- Everything is an object
- One single model
- Single inheritance
- Public methods
- Protected attributes
- Classes are simply objects too
- Class is instance of another class
- One unique method lookup
look in the class of the receiver