Version 35 of Smalltalk

Updated 2007-01-04 16:44:19 by suchenwi

Smalltalk [L1 ] is a pure object environment and programming language. Read the link to learn more.

Smalltalk is the oldest mature pure object-oriented language. It is brilliant, simple, and has only a few keywords. It is similar to Tcl in that the control structures are not part of language.

Almost all good things known in new hype-languages come from Smalltalk. That is

  • virtual machine
  • garbage collector
  • reflection (introspection)
  • dynamic object system (object can change the class, metaclasses)
  • Integrated Development Environment

Also many popular program-techniques were developed under Smalltalk first. That is Extreme Programming (with Unit-tests), Refactoring Tools, Visual Programming, MVC (Model / View / Controller).

Smalltalk has also well designed standard libraries (Collections, Process Control, I/O).

Squeak [L2 ] is a popular Smalltalk implementation with an active community, and several interesting features. If you want to play with Smalltalk, Squeak is a good start. - TP, whose first OO language was Smalltalk.

Why is not Smalltalk the first most popular object-oriented program language? The reasons could be:

  • for 30 years computers were too slow for virtual machines.
  • the first smalltalk systems was too expensive for normal folk.
  • smalltalk was too closed (not open) to another systems or languages.
  • has no types. Some managers believe that typed languages can save them from ignorance.
  • it is too mature for making big money with consulting, i.e., it is on the trailing curve of the hype bandwagon.
  • jcw adds another - more technical - reason: deployment can be tricky...

RLH Deployment is a lot better in Smalltalk (though still a little clunky). Here [L3 ] is a little walkthough on how a developer decided between C++ and Smalltalk.

XOTcl is an object-oriented extension for Tcl that has some characteristics from Smalltalk. It is also dynamic and has metaclasses and also have the same feeling. XOTclIDE provide Smalltalk-like IDE (Squeak, Version Control as in Envy)


Talking of syntax, here's a snippet from [L4 ] - double-quoted strings are just comments:

       7   "a number"
       $z  "a character"
       'colourless ideas sleep furiously'   "a string"
       #(#tom #dick #harry)  "an array of 3 components"
       #(# one 'should shower at least' 3 'times a week')

# before a string turns it into a symbol (like quote in LISP); #(...) denotes what we'd call a list. RS can't help finding Tcl simpler, and better-looking...

Lars H: Does the # work like / in Postscript? In that language, /tom is just a name whereas tom is a command. Anyhow I agree Tcl looks better. - RS: Yes, #tom is the symbol tom, 'tom' is a string constant, and tom either variable or method/keyword.

Let see some sample program to show all main Smalltalk syntax and look and feel.

  | myVar myVar2 |   " Variable Definition"
  myVar := SampleClass new. "Create Instance of Class Sample Class.
                                  new is simple method call on object SampleClass not special operator
                                  Everything is object"

  myVar setSample: 1.  "call method setSample: with one parameter"

  myVar setSample: 2 with: 3. "call method setSample:with: with two parameters"

  "method chaning java myVar.getAnotherObjekt().callThisObjectWith(23)"
  myVar getAnotherObjekt callThisObjectWith: 23. 

  "Now Blocks"
  myVar isRead ifTrue: [Transcpript show: 'I am Ready] ifFalse: [Transcript show: 'Not Ready']

  "Or somethig like C operator ? : "
  myVar := myVar isRead ifTrue: [1] ifFalse: [2].

  "Collection"
  myVar := Array new.

  "Write Collection on stdout"
  myVar do: [:each | Transcript show: each printString].

  "Blocks are also objects. That can take parameters. see also Ruby language"

  "Blocks can be used do define new control stuctures or something like handlers"
  myVar := [:par1 | Transcript show: par1].

  "Evalute Block."
  myVar value: 2.

  "same as"
  [:par1 | Transcript show: par1] value: 2

  "method cascading"
  myVar method1; method2; method3

  "equal to"
  myVar method1. myVar method2. myVar method3

Yes. It looks strange. It is not like Fortran, C, C++, Java or C#. It is also not like basic, perl, bash, tcl....


Shin The Gin (2007-01-4) - If you are addicted to the convenience of a common Smalltalk environment, give Tcltalk a try! You'll find workspaces and browsers and even logging of changes, all without object orientation.


RS: Could one say that Smalltalk's "blocks with parameters" correspond to Tcl's upcoming apply lambdas (starting from 8.5)?


[ Category Language | Category Object Orientation ]