Smalltalk

is a pure object environment and programming language.

Reference edit

The Early History Of Smalltalk, Alan C. Kay, 1993
Alan Kay - 2012 SCIx Keynote Presentation, 2012

Description edit

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 the language.

Almost all good things known in currently-hyped languages come from Smalltalk. For example:

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:

Extreme Programming: (with Unit-tests)
Refactoring Tools
Visual Programming
Model / View / Controller

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

TpP: My first OO languge was Smalltalk. Squeak

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.

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

for 30 years computers were too slow for virtual machines.
the first Smalltalk systems were too expensive for normal folk.
Smalltalk was too closed (not open) to another systems or languages.
No types. Some managers believe that typed languages can save them from ignorance.
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 [1] is a little walkthough on how a developer decided between C++ and Smalltalk.

Talking of syntax, here's a snippet from [2] - 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 # 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)?

NEM: Yes and no. As I understand it, Smalltalk blocks are full lexical closures, so they are a bit more powerful than Tcl's lambdas. Smalltalk is actually quite a nice functional programming language as well as OO.

RJH 2013-05-15:

Forgive my confusion; but the original author appears to claim that 'garbage collection' originated in smalltalk. I was under the impression that smalltalk originated somewhere around the early 1970s and that garbage collection originated with Mr. McCarthy's LISP in the late 1950s...

Have I misunderstood the history - or is the claim that smalltalk originated GC a little overenthusiastic?

Thanks, R.

Reference edit

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