Updated 2014-12-01 19:22:09 by pooryorick

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:

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].
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.

See Also  edit

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 provides Smalltalk-like IDE (Squeak, Version Control as in Envy)