Powerful DSL engineering with Smalltalk

Transcription

1 Powerful DSL engineering with Smalltalk Stéphane Ducasse Stéphane Ducasse 1

2 A word of introduction Reflective, metamodeler and happy programmer Wrote several books on Smalltalk Pharo by example, Squeak by Example,... Pushed Moose Building Pharo Maintained Squeak 2

3 RMOD INRIA Team Software evolution and software composition Axis 1: Maintaining large software systems Moose: a platform for reengineering, Axis 2: Modular and Secure Reflective languages Revisiting fundamental aspects of OO languages Traits (SUN Microsystems...), Classboxes Pharo open-source Smalltalk Starting to work on a secure reflective languages 3

4 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 About design and DSL 5

6 Good OOP design makes implicit explicit 6

7 Classes structure our vocabulary 7

8 Classes are recipients of message reaction 8

9 Boolean xor: eqv: storeon: and: or: iftrue:iffalse: & not iftrue: truealternativeblock iffalse: falsealternativeblock self subclassresponsibility False and: or: iftrue:iffalse: & not True and: or: iftrue:iffalse: & not iftrue: truealternativeblock iffalse: falsealternativeblock ^ truealternativeblock value iftrue: truealternativeblock iffalse: falsealternativeblock ^ falsealternativeblock value 9

10 Ternary logic Boolean: true, false, unknown 10

11 Focus on **your** domain Define domain elements as first class objects Long tradition in Smalltalk 11

12 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 Requirements for a real DSL Adequate syntax Capture intent/domain EXECUTABLE! Tools TestRunner Browsers Semantics versioning Debuggers! 13

14 Smalltalk is a modeling executable language Quite close from xactium 14

15 Smalltalk Modeling the world Simple syntax Trivial OO model Executable Full set of powerful tools 15

16 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 Date today is a unary message 17

18 1000 factorial is a unary message 18

19 1 / 3 is a binary message 19

20 1000 factorial / 999 factorial is a unary/binary messages 20

21 Color gray - Color white = Color black 21

22 Color r: 0 g: 0 b: 1 is a keyword-based message 22

23 From Java to Smalltalk postman.send(mail,recipient); 23

24 Removing postman.send(mail,recipient); 24

25 Removing unnecessary postman send mail recipient 25

26 But without losing information postman send mail to recipient 26

27 postman send: mail to: recipient postman.send(mail,recipient); 27

28 Tamagotchi Small entity Its own night and day cycle Eating, sleeping, been hungry, been satisfied Changing color to indicate its mood 28

29 Class Object subclass: #Tamagotchi instancevariablenames: tummy hunger daycount isnight' classvariablenames: '' pooldictionaries: '' category: TOMA' 29

30 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 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

32 Self-described 32

33 Implemented totally in itself extensible... 33

34 Vocabulary points 34

35 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 Internal Languages Ruby: rspec, rake JavaScript: jquery Smalltalk: Mondrian, Seaside, PetitParser + easy to implement, tool support, easily mixable 36

37 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 Mondrian metaphor: painting a view Composition with Red, Yellow and Blue Piet Mondrian (1921) 38

39 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 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 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 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 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

44 What about interaction? 44

45 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 Glamour Internal language to build data explorer/browser Component-based 46

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50 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 Seaside To build dynamic applications Applications in production since 2002 Natural Flow Reusable statefull components Secure by default Web

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54 value1 := self request: first number. value2 := self request: second number. self inform: value1 asnumber + value2 asnumber 54

55 Not concerned about HTTP No manual request parsing No XML configuration files 55

56 56 Source: stock.xchng, Al Nakib

57 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 html anchor callback: [ self inform: Hello World ]; with: Show Message Generates... <a href= /seaside/example1?_s=ru8zkgqjy0udx3kf &_k=k5eqyqke &32 >Show Message</a> 58

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60 WAComponent subclass: #Example2 instancevariablenames: 'english' classvariablenames: '' pooldictionaries: '' category: 'SeaExample' 60

61 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 Full hot on the fly debug Full integration with javascript Handling of the back button... 62

63 Slime Rule for checking validation of Seaside internal language 63

64 Mastering Embedded Languages!" #"$%& 64

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66 change semantics Adopt, Extend, Overload introduce new syntax change syntax & semantics 66

67 x = 1 x = 2 y = 1 Package Name (2, 1) y = 2 (1, 2) (2, 2)

68 abuilder row grow. abuilder row fill. abuilder column grow. abuilder column fill. x = 1 x = 2 y = 1 Package Name (2, 1) y = 2 (1, 2) (2, 2) 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; 68

69 row = grow. row = fill. x = 1 x = 2 y = 1 Package Name (2, 1) column = grow. column = fill. y = 2 (1, 2) (2, 2) (1, 1) = label text: [ :each each name ]; bordercolor: #black; borderwidth: 1. (1, 2) - (2, 1) = rectangle bordercolor: #black; borderwidth: 1; width: 200; height:

70 shape { } label { } rectangle { cols: #grow, #fill; rows: #grow, #fill; position: 1, 1; text: [ :each each name ]; bordercolor: #black; borderwidth: 1; position: 1, 2; colspan: 2; bordercolor: #black; borderwidth: 1; width: 200; x = 1 x = 2 y = 1 Package Name (2, 1) y = 2 (1, 2) (2, 2) 70

71 Homogeneous Tools 71

72 Domain-Specific 72

73 Source Smalltalk Semantic Bytecode Executable Code Parser Analysis Generation Code Traditional Smalltalk Compiler

74 Rules <parse> <transform> <attribute> <bytecode> Source Smalltalk Semantic Bytecode Executable Code Parser Analysis Generation Code Traditional Smalltalk Compiler

75 ... <complete> <highlight>... Rules <parse> <transform> <attribute> <bytecode> Source Smalltalk Semantic Bytecode Executable Code Parser Analysis Generation Code Traditional Smalltalk Compiler

76 ... <complete> <highlight>... Creole path Pidgin path Rules <parse> <transform> <attribute> <bytecode> Source Smalltalk Semantic Bytecode Executable Code Parser Analysis Generation Code Traditional Smalltalk Compiler

77 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 BNF ID ::= letter { letter digit } ; Ometa2 id = letter (letter digit)* PetitParser id := #letter asparser,! (#letter asparser / #digit asparser) star 78

79 Smalltalk is a serious player in DSL Trivial model Trivial syntax Internal DSLs Embedded DSLs Full tool support Extensible (build your own) Executable 79

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