CS 403: Programming Languages

Lecture 5

Fall 2003

Department of Computer Science

University of Alabama

Joel Jones

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Outline

Introduction to Smalltalk—What, Why, How

Introduction to Squeak

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What is different about Smalltalk?

Everything is an object A real integrated development

environment Carefully integrated classes and syntax Dynamically typed Simple syntax

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Why learn Smalltalk? Nobody uses it. Yeah, nobodys like:

FedEx Ericsson Chrysler Deutsche Bank Dunn and Bradstreet Wisconsin Department of

Revenue Geico Direct John Deere

Texas Instruments Nokia Mitsubishi Volkswagen Bell Atlantic NYNEX Bell South MCI USWest

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History of Smalltalk

A few links http://www.ayers.je/smalltalk/smalltalkhistory

.html http://www.mojowire.com/

TravelsWithSmalltalk/DaveThomas-TravelsWithSmalltalk.htm

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Are you serious? But hopefully you will get a feel for why I

like Smalltalk so much and Why we will be looking at Smalltalk a little

further

Will I be a good Smalltalk programmer by the end of the lecture?

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Why do I care about the properties mentioned earlier? Carefully integrated classes and syntax

for (Iterator i = myCollection.iterator(); i.hasNext(); ) { ItemType myItem = (ItemType) i.next(); myItem.something();}

myCollection do [:myItem | myItem something]

Java

Smalltalk

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Why do I care about the properties mentioned earlier? Everything is an object

for (int i = 0; i < myArray.length; i++) { ItemType myItem = myArray[i]; myItem.something();}

myArray do [:myItem | myItem something]

Java

Smalltalk • Pair Up:

• What other property is exhibited here?

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How the heck did that Smalltalk code work? Simple stuff first

myItem something is a simple message send with no arguments

A little harder myCollection do: [ … ] is a message send

with one keyword with an argument Even harder

[…] is a block, which is a closure, a thunk with arguments, an anonymous inner class, a function pointer with lexical capture, etc.

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Everything is an Object I wasn’t kidding The block is an object All loops and control structures in

Smalltalk are objects Once you learn them, the collection

classes mean you don’t have to write the same kind of loop infrastructure over and over again

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Control methods Collections

do: select: collect: detect: detect: ifNone: inject: into: reject:

Boolean ifTrue: ifTrue: ifFalse: ifFalse: ifFalse: ifTrue:

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What is the Smalltalk programming environment like?

We will be using Squeak, a freely available implementation

We’ll be looking at it right now. A quick reference can be found at:

http://www.mucow.com/squeak-qref.html

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References

Download implementation, etc. www.squeak.org

www.smalltalk.org Smalltalk idioms and conventions

http://www.angelfire.com/tx4/cus/notes/smalltalk.html

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Next two classes

I will be out of town Meet at normal class time and place Someone will have lab assignments for

you to do on Smalltalk http://www.mucow.com/squeak-qref.html