TicTacToe Game in Pharo Smalltalk 11:57 AM

For an absolute pharo/smalltalk beginner, I think this would be a good place to start with. This is a simple TicTacToe implementation with just three classes : TicTacToe, TicTacToeCell and TicTacToeModel using Morphs. Works on MVC based architecture with view and model separate (no specific class for controller though).

Object subclass: #TicTacToe
instanceVariableNames: 'container model'
classVariableNames: ''
poolDictionaries: ''
category: 'VK-Games'

initialize 
container := Morph new 
              layoutPolicy: TableLayout new; 
              color: Color transparent.
model := TicTacToeModel new:3.
self addRows.
self addControls.
^self.

addRows
| rowMorph aCell rowCol |
1 to:3 do:[ :row |
rowMorph := Morph new layoutPolicy: RowLayout new.
1 to: 3 do: [ :col |
aCell := TicTacToeCell new.
aCell setModel: (model) row: row col: col.
rowMorph addMorph: aCell.
].
container addMorph: rowMorph.
]

addControls
| rowMorph newGameButton exitGameButton |
rowMorph := Morph new 
             layoutPolicy: RowLayout new; 
             color: Color transparent.
newGameButton := self createCtrlLabelled: 'New'      onClickExecutes: [self restart].
exitGameButton := self createCtrlLabelled: 'Exit'  onClickExecutes: [container delete].
rowMorph addMorph: exitGameButton.
rowMorph addMorph: newGameButton.
container addMorph: rowMorph.

createCtrlLabelled: aString onClickExecutes: aBlock
| aCtrlButton |
aCtrlButton := SimpleButtonMorph new label: aString.
aCtrlButton color: (Color black alpha: 0.2).
aCtrlButton extent: 60@30.
aCtrlButton on: #click send: #value to: aBlock.
^aCtrlButton.

open 
container openInWorld.

restart
container delete.
Smalltalk garbageCollect.
TicTacToe new open.

*****************************************

SimpleButtonMorph subclass: #TicTacToeCell
instanceVariableNames: 'parentModel rowNum colNum'
classVariableNames: ''
poolDictionaries: ''
category: 'VK-Games'





initialize 

super initialize.

self label: ''.

self extent: 40@40.

self on: #click send: #value to: (self onClickExecutionBlock).

^self.




setModel: ticTacToeModel row: aRow col: aCol

parentModel := ticTacToeModel.

rowNum := aRow.

colNum := aCol.




onClickExecutionBlock

^[

(self label size) == 0

ifTrue:[

self label: (parentModel updateAtRow: rowNum 
                Col: colNum).

parentModel checkWinCondition.

self extent: 40@40.

].

 ]



***************************************** 



Matrix subclass: #TicTacToeModel

instanceVariableNames: 'filledCellCount currentFill winner'

classVariableNames: ''

poolDictionaries: ''

category: 'VK-Games'

initialize 

super initialize.

filledCellCount := 0.

currentFill := nil.

winner := nil.

updateAtRow: r Col: c

currentFill == nil

ifTrue:[ currentFill := 'X'. ]

ifFalse:[

currentFill == 'X'

ifTrue: [ currentFill := 'O'. ]

ifFalse: [ currentFill := 'X'. ]

].

self at: r at: c put: currentFill.

filledCellCount := filledCellCount + 1.

^currentFill.

checkWinCondition

filledCellCount >= 5 "for optimization. Win can occur minimum at 5th turn"

ifTrue: [

Transcript show: 'Yes'.

1 to: 3 do: [:idx |

self checkWinConditionInRow: idx.

self checkWinConditionInColumn: idx.

].

self checkWinConditionInDiagonals.

].

checkWinConditionInRow: rowNum

|set|

winner isNil

ifTrue: [

set := (self atRow: rowNum) asSet.

self checkWinConditionInSet: set

].

^winner.

checkWinConditionInColumn: colNum

|set|

winner isNil

ifTrue: [

set := (self atColumn: colNum) asSet.

self checkWinConditionInSet: set.

].

^winner.

checkWinConditionInDiagonals

|set1 set2 |

winner isNil

ifTrue: [

set1 := (self diagonal) asSet.

set2 := Set newFrom: {(self at: 1 at: 3). (self at: 2 at: 2). (self at: 3 at: 1)} asOrderedCollection.

self checkWinConditionInSet: set1.

self checkWinConditionInSet: set2.

].

^winner.

checkWinConditionInSet: aSet

aSet size == 1

ifTrue: [

(aSet includes: 'X')

ifTrue: [winner := 'P1'. Transcript open. Transcript show: 'Player 1 is the winner!!'.].

(aSet includes: 'O')

ifTrue: [winner := 'P2'.  Transcript open. Transcript show: 'Player 2 is the winner!!'.].

].




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Coffee with Linux #2 - The Shell 5:33 AM

Generally, users interact with the Operating System by clicking on icons, menus and buttons. This is called Graphical User Interface (GUI). Apart from this, there is also an other way to interact with the computer using a command line interface (CLI) which is purely by typing in commands to get the task done. Think of it the DOS command prompt in the world of Windows. One can open Notepad application either by selecting it from the start menu or by simple typing in notepad on the windows prompt. In a parallel context, the command line interface on Linux that enables human-machine interaction is called 'The Shell'. That being said, it is not technically correct to draw a comparison between the Windows DOS prompt and the Linux shell because the shell is capable of doing much much much more than what can be done from a regular dos prompt on windows.

The shell has many variants, some of which are 

• C Shell
• Korn
• Bash
• Z shell

Bash is used as a default for many Linux distros that are available today. In almost all Linux distros you find an option called terminal emulator (or simply the terminal). The terminal is merely a window that runs the shell program within it.

Standard input & Standard output

What you type in to the terminal on Linux is called the standard input and the output of the command typed in is called the standard output. This happens via streams. Whatever is typed in, is taken onto a stream (stdin) which is a continuous set of bytes, likewise the output is also written onto a stream (stdout) that is by default shown on the screen. You can redirect this stream, the standard output on screen onto a file or anywhere else. Example :

$ ls > outputOfLSCommand.txt


Speaking of streams there is a separate stream for carrying the error output (stderr). Likewise you can also redirect the standard input from a file instead of defaulting it to the keyboard.

Piping the output

Just the way the output is redirected, the user can also pipe the output. Piping generally happens when the output of one command is given as input to an other command. Example

$ ls | rev


In this command the output of list directories command as a String is given as an input to the rev (the reverse) command which displays the output text in a reversed way.

*********** End of Tutorial 2 ***********

See Introduction Tutorial 1: Coffee with Linux #1 - Head Start

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Find RSS Feed URL of a Webpage 5:30 AM

Given a URL of a web page, one can programatically search through the meta tags of the webpage's content for alternate URL links (like atom or RSS feed links for the same) to thereon further use them to parse and process the content of the webpage. Typically this is the way Google Reader works. Here I present a very simple implementation of the same in pharo smalltalk.


Object subclass: #RSSReader
instanceVariableNames: ''
classVariableNames: ''
poolDictionaries: ''
category: 'VamsiExperiments'


getURLContent: url
  "## Comment : Supply the url String of the webpage, 
   ## example: http://nerdysermons.blogspot.in"
| urlContent |
urlContent := (url asUrl retrieveContents contents asString).
^urlContent



findAlternateLinksInUrlContent: urlContent
  "## Comment : The above fetched page content to 
   ## be passed here to get an ordered collection 
   ## of alternate links"      
| links|
links := OrderedCollection new.
urlContent linesDo:  [:line |
(line findString: '<link rel="alternate"') > 0
ifTrue: [
links add: (line findTokens:'"' includes: 'http://').
].  
].
^links.


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