<s5>Æliens</s5> -- slide(s)

Smalltalk -- a radical change in programming

A


  1972  Dynabook -- Alan Kay
  1976  SmallTalk76
  1980  SmallTalk80
  1990  ObjectWorks/SmallTalk -- VisualWorks

Design principles -- rapid prototyping

uniform object model -- control
dynamic typing -- flexible
standard libraries -- functionality

slide: The language Smalltalk

Terminology

Smalltalk

literal -- constants
object -- action by messages
class -- collection of protocols
protocol -- related methods
category -- collection of classes

slide: Smalltalk -- terminology

Literal constants

number -- 1, 34.6, 8r24
character -- $a, $b, ...
string -- "this is a string"
symbol -- #Float
byte array -- # [0 255 2 7]
array of literals -- # (12.1 # ($a $b))

slide: Smalltalk -- expressions (1)

Assignment

$aVar := 1.$

Variables

temporary, instance, class, pool, global

Block expressions

$[ :arg | expression ]$

slide: Smalltalk -- expressions (2)

Message expressions

unary, binary, keyword

Unary

$1.0 sin$ , $Random new$

Binary

arithmetic -- $ctr + 1$
comparison -- $aVar >= 200$
combination -- $100 @ 200$
association -- $# Two -> 2$

slide: Smalltalk -- expressions (3)

Keyword methods


    (i <= 7) 
          ifTrue: [ m:= "oke" ]
          ifFalse: [ ... ]

Control structures

conditional -- $ifTrue: ifFalse:$
iteration -- $whileTrue:$
looping -- $to: by: do: [ :i | ... ]$

slide: Smalltalk -- control

Object -- behavior

instance variables, methods

Class -- description

class variables, class methods

Self -- self reference

super for ancestors

slide: Smalltalk -- objects (1)

Example -- class


  Behavior subclass: #Ctr
  instanceVariableNames: 'value'
  Ctr methodsFor: 'initialization'
     initialize
  	value := 0.
  Ctr methodsFor: 'modifications'
     add: aValue
  	value := value + aValue.
  Ctr methodsFor: 'inspection'
     value
  	^value

slide: Smalltalk -- objects (2)

Class description -- meta class


  Ctr class
  instanceVariableNames: ''
  Ctr class methodsFor: 'instance creation'
  	new
  		^super new initialize

slide: Smalltalk -- objects (3)

Inheritance


    Object
      Magnitude
         ArithmeticValue
            Number
               Integer

slide: Smalltalk -- inheritance


  Model subclass: #Ctr    Model  
    ...
    initialize
      value := 0.
      TV open: self.
    ...
    add: anInt  
      value := value + anInt.
      self changed: #value.

slide: Smalltalk -- technology (1)


  View subclass: #TV    View  
  instanceVariableNames: ''
  TV methodsFor: 'updating'
  update: aValue
       Transcript show: 'ok'; cr .
  TV class
  instanceVariableNames: ''
  TV class methodsFor: 'instance creation'
       open: aCtr
  	self new model: aCtr

slide: Smalltalk -- technology (2)

The language Smalltalk

A

design principles -- prototyping
terminology -- object, class, protocols
syntax -- method expressions
objects -- self reference
inheritance -- class hierarchy
techniques -- MVC paradigm

slide: Smalltalk -- summary

Æliens

2009

Smalltalk -- a radical change in programming

Design principles -- rapid prototyping

Terminology

Literal constants

Assignment

Variables

Block expressions

Message expressions

Unary

Binary

Keyword methods

Control structures

Object -- behavior

Class -- description

Self -- self reference

Example -- class

Class description -- meta class

Inheritance

Model

View

The language Smalltalk