Pharo Hands-On: 02 syntax
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This document provides an overview of the syntax and core concepts in Pharo. It discusses that Pharo has no constructors, types, interfaces, packages, or parametrized types. The core abstractions are objects like strings, numbers, collections, and blocks. Messages can be unary, binary, or take keywords. Control flow uses conditionals that send messages to booleans. Common loops include timesRepeat:, to:do:, and collect:. Defining methods involves subclassing and specifying instance/class variables.
![Block: Lambda Expressions
[ :x | x + 2 ] value: 5
-> 7
!
anonymous method
[ ]
:x is the block arguments](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-15-320.jpg)
![Blocks can be stored
| b |
b := [ :x | x + 2 ].
b value: 5
-> 7
b value: 33
-> 35](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-16-320.jpg)
![Conditionals: ifTrue:ifFalse:
Booleans are objects
Conditional are messages sent to booleans or block
!
!
initialAnswer := fullName isEmptyOrNil
ifTrue: ['FirstnameLastname' translated]
ifFalse: [fullName].](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-17-320.jpg)
![ifTrue:
forceItalicOrOblique
self slantValue = 0 ifTrue: [ slantValue := 1 ]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-18-320.jpg)
![ifFalse:ifTrue:
index = 0
ifFalse: [values at: index]
ifTrue: [self privateAt: key put: aBlock value]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-19-320.jpg)
![ifEmpty:
(myProtocol
ifEmpty: ['As yet unclassified’]
!
self listItems
ifNotEmpty: [ :aList | aList at: currentIndex ]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-20-320.jpg)
![Use [ ] when you do not know how many time it is
executed.
( x isNil) ifTrue: [ .... ]
( ...) vs. [ ]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-21-320.jpg)
![Some loops
4 timesRepeat: [ self doSomething ]
0 to: 100 [ :i | ... ]
0 to: 100 by: 3 [ :i | ... ]
aCol do: [:each | ... ]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-22-320.jpg)
![Some loops: to:by:do:
| sum |
0 to: 100 by: 3 [ :i | sum= sum + i ]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-23-320.jpg)
![#(15 10 19 68) do:
[:i | Transcript show: i ; cr ]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-24-320.jpg)
![#(15 10 19 68) do:
[:i | Transcript show: i ; cr ]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-25-320.jpg)
![#(2 -3 4 -35 4) collect: [ :each| each abs]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-26-320.jpg)
![#(2 -3 4 -35 4) collect: [ :each| each abs]
> #(2 3 4 35 4)](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-27-320.jpg)
![Defining a method
(2@3) <= (5@6)
!
<= aPoint
"Answer whether the receiver is neither below nor to
the right of aPoint."
^ x <= aPoint x and: [y <= aPoint y]](https://image.slidesharecdn.com/02-syntax-150404120255-conversion-gate01/85/Pharo-Hands-On-02-syntax-28-320.jpg)
Pharo Hands-On: 02 syntax
- 1. Pharo: Syntax in a Nutshell S. Ducasse http://www.pharo.org
- 2. No constructors No types declaration No interfaces No packages/private/protected No parametrized types No boxing/unboxing And really powerful Less is More
- 4. A Pure OO World Only objects! mouse, booleans, arrays, numbers, strings, windows, scrollbars, canvas, files, trees, compilers, sound, url, socket, fonts, text, collections, stack, shortcut, streams, …
- 5. 3 kinds of messages Unary messages Binary messages Keywords messages 5 factorial! Transcript cr 3 + 4 2 between: 0 and: 5! ! Transcript show: 'hello world'
- 8. postman send mail recipient
- 9. postman send mail to recipient
- 10. postman send: mail to: recipient
- 11. () > Unary > Binary > Keywords ! 1 class maxVal + 1 (1 class maxVal + 1) class 1 class maxVal raised: 3+ 2
- 12. Typical Expression ZnEasy client url: 'http://bugs.pharo.org/issues/name/', text asString; get; response.
- 13. Some basic objects String: 'a string' Symbole (unique String): #aSymbol Character: $A Array: #(1 2 3) { 1 . 2 . 3} OrderedCollection: OrderedCollection new add: 35; add: 45; yourself Set: Set new add: 1; add: 2; yourself
- 14. yourself? Set new add: 1; add: 2; yourself is equivalent to | s | s := Set new. s add: 1; add: 2. s
- 15. Block: Lambda Expressions [ :x | x + 2 ] value: 5 -> 7 ! anonymous method [ ] :x is the block arguments
- 16. Blocks can be stored | b | b := [ :x | x + 2 ]. b value: 5 -> 7 b value: 33 -> 35
- 17. Conditionals: ifTrue:ifFalse: Booleans are objects Conditional are messages sent to booleans or block ! ! initialAnswer := fullName isEmptyOrNil ifTrue: ['FirstnameLastname' translated] ifFalse: [fullName].
- 18. ifTrue: forceItalicOrOblique self slantValue = 0 ifTrue: [ slantValue := 1 ]
- 19. ifFalse:ifTrue: index = 0 ifFalse: [values at: index] ifTrue: [self privateAt: key put: aBlock value]
- 20. ifEmpty: (myProtocol ifEmpty: ['As yet unclassified’] ! self listItems ifNotEmpty: [ :aList | aList at: currentIndex ]
- 21. Use [ ] when you do not know how many time it is executed. ( x isNil) ifTrue: [ .... ] ( ...) vs. [ ]
- 22. Some loops 4 timesRepeat: [ self doSomething ] 0 to: 100 [ :i | ... ] 0 to: 100 by: 3 [ :i | ... ] aCol do: [:each | ... ]
- 23. Some loops: to:by:do: | sum | 0 to: 100 by: 3 [ :i | sum= sum + i ]
- 24. #(15 10 19 68) do: [:i | Transcript show: i ; cr ]
- 25. #(15 10 19 68) do: [:i | Transcript show: i ; cr ]
- 26. #(2 -3 4 -35 4) collect: [ :each| each abs]
- 27. #(2 -3 4 -35 4) collect: [ :each| each abs] > #(2 3 4 35 4)
- 28. Defining a method (2@3) <= (5@6) ! <= aPoint "Answer whether the receiver is neither below nor to the right of aPoint." ^ x <= aPoint x and: [y <= aPoint y]
- 29. Class definition Object subclass: #Point instanceVariableNames: 'x y' classVariableNames: '' category: 'Graphics-Primitives'
- 30. Conclusion Messages (unary, binary, keywords) Blocks Methods are named blocks