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Smalltalk

Smalltalk. Mark Colangelo CMSC-631, Fall 2002 10 December 2002. History of Smalltalk. Alan Kay designed and build the first OOP-based personal Computer called FLEX in 1967-68 In 1967 Simula 67 was designed

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Smalltalk

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  1. Smalltalk Mark Colangelo CMSC-631, Fall 2002 10 December 2002

  2. History of Smalltalk • Alan Kay designed and build the first OOP-based personal Computer called FLEX in 1967-68 • In 1967 Simula 67 was designed • In 1972 Alan Kay and other and XEROX PARC Created Smalltalk 72 with roots tied to Simula 67 • Followed by Smalltalk 76 (Completely OOPL) • Followed by Smalltalk 80 which became available as the first commercial release of Smalltalk

  3. Smalltalk in the Real World • Financial • Chubb • Chrysler • Dunn and Bradstreet, several other • Manufacturing and Engineering • Texas Instruments • Romax (Simulation Software)

  4. Free Implemenations of Smalltalk • Squeak (Smalltalk for Win , Mac and others) • http://www.squeak.org/download/index.html • GNU Smalltalk (Unix systems only) • http://www.gnu.org/software/smalltalk/smalltalk.html

  5. Installation of Squeak • Installation of Squeak is trivial • Download zip file • Squeak3.2.image • Squeak3.2.changes • SqueakV3.sources • Squeak VM for your system, version 3.2 • Doubleclick Squeak image. No other installation is required

  6. Squeak Install Files

  7. Squeak Desktop

  8. Hello World

  9. Exending Hello World hello 1 to: 3 do: [:i | (Transcript show: 'Hello World') cr] Gives: Hello World Hello World Hello World

  10. Adding Logic to Hello World hello: times (times > 100) ifTrue: [ Transcript show: 'You will get bored!'] ifFalse: [1 to: times do: [:i | (Transcript show: 'Hello World') cr]]

  11. Final Hello World hello: times say: text (times > 100) ifTrue: [ Transcript show: 'You will get bored!'] ifFalse: [1 to: times do: [:i | (Transcript show: text) cr]]

  12. Syntax Observations • Any variable can store any object. Object keeps track of what it is. • Could pass an integer into the text parameter. No error until the Transcript tried to show it.

  13. Messaging • Always pass messages to an object • the colon syntax for parameter passing looks a lot like the colon syntax for loops--and logic, for that matter. That's because it's exactly the same. • hello:say, ifTrue:ifFalse: and to:do are all messages.

  14. Blocks of Code are Objects • [:i | (Transcript show: text) cr] is an object • Code block can be passed as an argument to to:do: • Transcript is a global variable that contains an object which understands the show: message. • In addition to show:, the Transcript object understands the message cr, which puts a newline in the Transcript window.

  15. References • Smalltalk home page • www.smalltalk.org • Squeak home page • www.squeak.org • Smalltalk Industry Council home page • www.whysmalltalk.com

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