Stéphane Ducasse: Powerful DSL engineering with Smalltalk
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This document discusses domain-specific languages (DSLs) and how Smalltalk is well-suited for building DSLs. It provides examples of internal DSLs built in Smalltalk, including Mondrian for visualization, Glamour for data exploration, and Seaside for web applications. It also discusses techniques for mastering embedded DSLs, such as adopting, extending, or overloading syntax and semantics. Finally, it notes how Smalltalk provides homogeneous tools that are useful for building DSLs.
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Stéphane Ducasse: Powerful DSL engineering with Smalltalk
- 1. Stéphane Ducasse Stéphane Ducasse stephane.ducasse@inria.fr http://stephane.ducasse.free.fr/ RMod Powerful DSL engineering with Smalltalk 1
- 2. S.Ducasse RMod A word of introduction Reflective, metamodeler and happy programmer Wrote several books on Smalltalk Pharo by example, Squeak by Example, ... Pushed Moose http://www.moosetechnology.org Building Pharo http://www.pharo-project.org Maintained Squeak http://www.squeak.org 2
- 3. S.Ducasse RMod RMOD INRIA Team Software evolution and software composition Axis 1: Maintaining large software systems Moose: a platform for reengineering, http://moosetechnology.com Axis 2: Modular and Secure Reflective languages Revisiting fundamental aspects of OO languages Traits (SUN Microsystems...), Classboxes Pharo open-source Smalltalk http://www.pharo-project.org Starting to work on a secure reflective languages 3
- 4. S.Ducasse RMod Roadmap A word about design Smalltalk an executable modeling language Internal DSLs industrial examples Mondrian Glamour Seaside Helvetia: mastering embedded languages Tools: PetitParser Conclusion 4
- 5. S.Ducasse RMod About design and DSL 5
- 6. S.Ducasse RMod Good OOP design makes implicit explicit 6
- 7. S.Ducasse RMod Classes structure our vocabulary 7
- 8. S.Ducasse RMod Classes are recipients of message reaction 8
- 9. S.Ducasse RMod 9 Boolean xor: eqv: storeOn: and: or: ifTrue:ifFalse: & not | False and: or: ifTrue:ifFalse: & not | True and: or: ifTrue:ifFalse: & not | ifTrue: trueAlternativeBlock ifFalse: falseAlternativeBlock self subclassResponsibility ifTrue: trueAlternativeBlock ifFalse: falseAlternativeBlock ^ trueAlternativeBlock value ifTrue: trueAlternativeBlock ifFalse: falseAlternativeBlock ^ falseAlternativeBlock value
- 10. S.Ducasse RMod Ternary logic Boolean: true, false, unknown 10
- 11. S.Ducasse RMod Focus on **your** domain Define domain elements as first class objects Long tradition in Smalltalk 11
- 12. S.Ducasse RMod Exploratory modeling Extreme/agile modeling One domain expert One developer Pair-programming with the domain expert Using the domain expert vocabulary 2007 SAP Experience with Smalltalk 12
- 13. S.Ducasse RMod Requirements for a real DSL Adequate syntax Capture intent/domain EXECUTABLE! Tools TestRunner Browsers Semantics versioning Debuggers! 13
- 14. S.Ducasse RMod Smalltalk is a modeling executable language Quite close from xactium 14
- 15. S.Ducasse RMod Smalltalk Modeling the world Simple syntax Trivial OO model Executable Full set of powerful tools 15
- 16. S.Ducasse RMod A Simple and Pure Model Everything is an object (no primitive) Only message passing (virtual) Public methods/Private attributes Single inheritance Class extension (Program slices) Closures 16
- 17. S.Ducasse RMod Date today is a unary message 17
- 18. S.Ducasse RMod 1000 factorial is a unary message 18
- 19. S.Ducasse RMod 1 / 3 is a binary message 19
- 20. S.Ducasse RMod 1000 factorial / 999 factorial is a unary/binary messages 20
- 21. S.Ducasse RMod Color gray - Color white = Color black 21
- 22. S.Ducasse RMod Color r: 0 g: 0 b: 1 is a keyword-based message 22
- 23. S.Ducasse RMod From Java to Smalltalk postman.send(mail,recipient); 23
- 25. S.Ducasse RMod Removing unnecessary postman send mail recipient 25
- 26. S.Ducasse RMod But without losing information postman send mail to recipient 26
- 27. S.Ducasse RMod postman send: mail to: recipient postman.send(mail,recipient); 27
- 28. S.Ducasse RMod Tamagotchi Small entity Its own night and day cycle Eating, sleeping, been hungry, been satisfied Changing color to indicate its mood 28
- 29. S.Ducasse RMod Class Object subclass: #Tamagotchi instanceVariableNames:‘tummy hunger dayCount isNight' classVariableNames: '' poolDictionaries: '' category: ’TOMA' 29
- 30. S.Ducasse RMod initialize “Initialize the internal state of a newly created tomagoshi” super initialize. tummy := 0. hunger := 2 atRandom + 1. self dayStart. self wakeUp dayStart night := false. dayCount := 10 30
- 31. S.Ducasse RMod timePass "Manage the night and day alternance and digestion" Beeper beep. dayCount := dayCount -1. dayCount isZero ifTrue:[ self nightOrDayEnd. dayCount := 10]. self digest digest "Digest slowly: every two cycle, remove one from the tummy” (dayCount isDivisibleBy: 2) ifTrue: [ tummy := tummy -1] 31
- 33. S.Ducasse RMod Implemented totally in itself extensible... 33
- 35. S.Ducasse RMod External Languages Tools: make, flex, yacc Data: awk, sed, XPath, Regular Expressions, SQL + expressive, full control - expensive to implement, no tools, hard to pass data around 35
- 36. S.Ducasse RMod Internal Languages Ruby: rspec, rake JavaScript: jQuery Smalltalk: Mondrian, Seaside, PetitParser + easy to implement, tool support, easily mixable 36
- 37. S.Ducasse RMod Embedded Languages Language Workbenches: JetBrains MPS, Intentional Software + common infrastructure for different languages - new language, new tools, non-standard host language, targeted at domain experts (no programmers) 37
- 38. S.Ducasse RMod Mondrian metaphor: painting a view Composition with Red,Yellow and Blue Piet Mondrian (1921) 38
- 39. S.Ducasse RMod Mondrian a scriptable visualization “language” fast brainstorming of ideas interactive developed by Girba/Meer (SCG, Bern), maintained, optimized by Bergel (Pleaid, Santiago, Chile) heavily used by researchers in reengineering part of Moose 39
- 40. S.Ducasse RMod The view consists of nodes and edges view :=ViewRenderer new. view nodes: classes. view edges: classes from: [:each | each superclass] to: [:each | each]. view treeLayout. view open. 40
- 41. S.Ducasse RMod Visual representation is given by the shape view :=ViewRenderer new. view borderedRectangleShape height: [:each | each numberOfMethods]. view nodes: classes. view edges: classes from: [:each | each superclass] to: [:each | each]. view treeLayout. view open. 41
- 42. S.Ducasse RMod Blocks can be replaced by symbols view :=ViewRenderer new. view borderedRectangleShape height: #numberOfMethods. view nodes: classes. view edgesFrom: #superclass. view treeLayout. view open. 42
- 43. S.Ducasse RMod Nesting is done through blocks view :=ViewRenderer new. view borderedRectangleShape. view nodes: classes forEach: [:each | view nodes: each methods. view gridLayout]. view edgesFrom: #superclass. view treeLayout. view open. 43
- 45. S.Ducasse RMod Interaction is scriptable, too view :=ViewRenderer new. view2 :=ViewRenderer new. view interaction onSelect: [:each | each viewOn: view2]. view interaction popupView: [:each :aView | each viewOn: aView]. view nodes: ... 45
- 46. S.Ducasse RMod Glamour Internal language to build data explorer/browser Component-based 46
- 50. S.Ducasse RMod browser := GLMTabulator new. browser column: #one; column: #two. browser showOn: #one; using: [ browser table column: 'Character' evaluated: [ :each | each asString ]; column: 'ASCII' evaluated: [ :each | each asInteger printString ]; act: [:tree | tree inspect ] on: $i entitled: 'Inspect'; icon: [:x | MenuIcons helpIcon ]]. browser showOn: #two; from: #one; using: [ browser text ]. 50
- 51. S.Ducasse RMod Seaside To build dynamic applications Applications in production since 2002 Natural Flow Reusable statefull components Secure by default Web 2.0 http://www.seaside.st 51
- 54. S.Ducasse RMod value1 := self request:‘first number’. value2 := self request:‘second number’. self inform: value1 asNumber + value2 asNumber 54
- 55. S.Ducasse RMod 55 Not concerned about HTTP No manual request parsing No XML configuration files
- 57. S.Ducasse RMod html div id:‘list’; with: [ html span class:‘item’; with:‘Item 1’. html span class:‘item’; with:‘Item 2’ ] generates... <div id=”list”> <span class=”item”>Item 1</span> <span class=”item”>Item 2</span> </div> 57
- 58. S.Ducasse RMod html anchor callback: [ self inform:‘Hello World’ ]; with:‘Show Message’ Generates... <a href=”/seaside/example1 ?_s=Ru8ZKgqjy0uDX3kf &_k=K5EQyqKE &32”>Show Message</a> 58
- 60. S.Ducasse RMod WAComponent subclass: #Example2 instanceVariableNames: 'english' classVariableNames: '' poolDictionaries: '' category: 'SeaExample' 60
- 61. S.Ducasse RMod renderContentOn: html html form: [ html button callback: [english := true]; text: 'english'. html button callback: [self inFrench]; text: 'french'. html submitButton callback: [ english ifFalse: [self inform: 'Bonjour'] ifTrue: [self inform: 'Hello'] ] ; text: 'Say Hello' ] 61
- 62. S.Ducasse RMod Full hot on the fly debug Full integration with javascript Handling of the back button ... 62
- 63. S.Ducasse RMod Slime Rule for checking validation of Seaside internal language 63
- 66. S.Ducasse RMod change semantics introduce new syntax change syntax & semantics 66 Adopt, Extend, Overload
- 67. Package Name x = 1 y = 1 (2, 1) (2, 2)(1, 2) x = 2 y = 2
- 68. S.Ducasse RMod aBuilder row grow. aBuilder row fill. aBuilder column grow. aBuilder column fill. aBuilder x: 1 y: 1 add: (LabelShape new text: [ :each | each name ]; borderColor: #black; borderWidth: 1; yourself). aBuilder x: 1 y: 2 w: 2 h: 1 add: (RectangleShape new borderColor: #black; borderWidth: 1; width: 200; Package Name x = 1 y = 1 (2, 1) (2, 2)(1, 2) x = 2 y = 2 68
- 69. S.Ducasse RMod row = grow. row = fill. column = grow. column = fill. (1 , 1) = label text: [ :each | each name ]; borderColor: #black; borderWidth: 1. (1 , 2) - (2 , 1) = rectangle borderColor: #black; borderWidth: 1; width: 200; height: 100. Package Name x = 1 y = 1 (2, 1) (2, 2)(1, 2) x = 2 y = 2 69
- 70. S.Ducasse RMod shape { cols: #grow, #fill; rows: #grow, #fill; } label { position: 1 , 1; text: [ :each | each name ]; borderColor: #black; borderWidth: 1; } rectangle { position: 1 , 2; colspan: 2; borderColor: #black; borderWidth: 1; width: 200; Package Name x = 1 y = 1 (2, 1) (2, 2)(1, 2) x = 2 y = 2 70
- 74. Traditional Smalltalk Compiler Smalltalk Parser Semantic Analysis Bytecode Generation Executable Code Source Code <parse> <transform> <attribute> <bytecode> Rules
- 75. Traditional Smalltalk Compiler Smalltalk Parser Semantic Analysis Bytecode Generation Executable Code Source Code <parse> <transform> <attribute> <bytecode> Rules <complete> <highlight> ......
- 76. Traditional Smalltalk Compiler Smalltalk Parser Semantic Analysis Bytecode Generation Executable Code Source Code <parse> <transform> <attribute> <bytecode> Rules Pidgin path Creole path <complete> <highlight> ......
- 77. S.Ducasse RMod Scannerless Parsers combine what is usually done by two independent tools (scanner and parser) into one. This makes writing a grammar much simpler and avoids common problems when grammars are composed. Parser Combinators are building blocks for parsers modeled as a graph of composable objects; they are modular and maintainable, and can be changed, recomposed, transformed and reflected upon. Parsing Expression Grammars (PEGs) provide ordered choice. Unlike in parser combinators, the ordered choice of PEGs always follows the first matching alternative and ignores other alternatives. Valid input always results in exactly one parse-tree, the result of a parse is never ambiguous. Packrat Parsers give linear parse time guarantees and avoid common problems with left-recursion in PEGs. 77
- 78. S.Ducasse RMod BNF ID ::= letter { letter | digit } ; Ometa2 id = letter (letter | digit)* PetitParser id := #letter asParser , ! (#letter asParser / #digit asParser) star 78
- 79. S.Ducasse RMod Smalltalk is a serious player in DSL Trivial model Trivial syntax Internal DSLs Embedded DSLs Full tool support Extensible (build your own) Executable 79