Stéphane Ducasse
Stéphane [email protected]://stephane.ducasse.free.fr/
RMod
Powerful DSL engineering with Smalltalk
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A word of introduction
Reflective, metamodeler and happy programmer
Wrote several books on SmalltalkPharo by example, Squeak by Example, ...
Pushed Moose http://www.moosetechnology.org
Building Pharo http://www.pharo-project.org
Maintained Squeak http://www.squeak.org
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RMOD INRIA Team
Software evolution and software composition
Axis 1: Maintaining large software systemsMoose: a platform for reengineering, http://moosetechnology.com
Axis 2: Modular and Secure Reflective languages Revisiting fundamental aspects of OO languages Traits (SUN Microsystems...), ClassboxesPharo open-source Smalltalk http://www.pharo-project.orgStarting to work on a secure reflective languages
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Roadmap
A word about designSmalltalk an executable modeling languageInternal DSLs industrial examples
Mondrian GlamourSeaside
Helvetia: mastering embedded languagesTools: PetitParserConclusion
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About design and DSL
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Good OOP design makes implicit explicit
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Classes structure our vocabulary
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Classes are recipients of message reaction
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Boolean
xor:eqv:storeOn:and:or:ifTrue:ifFalse:¬ |
False
and:or:ifTrue:ifFalse:¬ |
True
and:or:ifTrue:ifFalse:¬ |
ifTrue: trueAlternativeBlock ifFalse: falseAlternativeBlock
self subclassResponsibility
ifTrue: trueAlternativeBlock ifFalse: falseAlternativeBlock
^ trueAlternativeBlock value
ifTrue: trueAlternativeBlock ifFalse: falseAlternativeBlock
^ falseAlternativeBlock value
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Ternary logic
Boolean: true, false, unknown
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Focus on **your** domainDefine domain elements as first class objects
Long tradition in Smalltalk
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Exploratory modeling
Extreme/agile modeling
One domain expertOne developer
Pair-programming with the domain expertUsing the domain expert vocabulary
2007 SAP Experience with Smalltalk
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Requirements for a real DSL
Adequate syntaxCapture intent/domainEXECUTABLE!Tools
TestRunnerBrowsersSemantics versioningDebuggers!
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Smalltalk is a modeling executable language
Quite close from xactium
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Smalltalk
Modeling the worldSimple syntaxTrivial OO modelExecutable Full set of powerful tools
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A Simple and Pure Model
Everything is an object (no primitive)Only message passing (virtual)Public methods/Private attributesSingle inheritanceClass extension (Program slices)Closures
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Date today
is a unary message
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1000 factorial
is a unary message
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1 / 3
is a binary message
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1000 factorial / 999 factorial
is a unary/binary messages
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Color gray - Color white = Color black
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Color r: 0 g: 0 b: 1
is a keyword-based message
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From Java to Smalltalk
postman.send(mail,recipient);
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Removing
postman.send(mail,recipient);
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Removing unnecessary
postman send mail recipient
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But without losing information
postman send mail to recipient
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postman send: mail to: recipient
postman.send(mail,recipient);
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Tamagotchi
Small entityIts own night and day cycleEating, sleeping, been hungry, been satisfiedChanging color to indicate its mood
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Class
Object subclass: #Tamagotchi instanceVariableNames: ‘tummy hunger dayCount isNight' classVariableNames: '' poolDictionaries: '' category: ’TOMA'
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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
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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]
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Self-described
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Implemented totally in itself
extensible...
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Vocabulary points
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External Languages
Tools: make, flex, yaccData: awk, sed, XPath, Regular Expressions, SQL
+ expressive, full control- expensive to implement, no tools, hard to pass data around
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Internal Languages
Ruby: rspec, rakeJavaScript: jQuerySmalltalk: Mondrian, Seaside, PetitParser
+ easy to implement, tool support, easily mixable
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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)
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Mondrian metaphor: painting a view
Composition with Red, Yellow and Blue Piet Mondrian (1921)
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Mondrian a scriptable visualization “language”fast brainstorming of ideasinteractive
developed by Girba/Meer (SCG, Bern), maintained, optimized by Bergel (Pleaid, Santiago, Chile)
heavily used by researchers in reengineeringpart of Moose
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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.
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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.
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Blocks can be replaced by symbols
view := ViewRenderer new.view borderedRectangleShape height: #numberOfMethods.view nodes: classes.view edgesFrom: #superclass.view treeLayout.view open.
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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.
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What about interaction?
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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: ...
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Glamour
Internal language to build data explorer/browserComponent-based
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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 ].
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Seaside
To build dynamic applications Applications in production since 2002Natural FlowReusable statefull componentsSecure by defaultWeb 2.0http://www.seaside.st
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value1 := self request: ‘first number’.value2 := self request: ‘second number’.self inform: value1 asNumber + value2 asNumber
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Not concerned about HTTP
No manual request parsing
No XML configuration files
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Sour
ce: s
tock
.xch
ng, A
l Nak
ib
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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>
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html anchor callback: [ self inform: ‘Hello World’ ]; with: ‘Show Message’
Generates...
<a href=”/seaside/example1 ?_s=Ru8ZKgqjy0uDX3kf &_k=K5EQyqKE &32”>Show Message</a>
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WAComponent subclass: #Example2 instanceVariableNames: 'english' classVariableNames: '' poolDictionaries: '' category: 'SeaExample'
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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' ]
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Full hot on the fly debugFull integration with javascriptHandling of the back button...
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Slime
Rule for checking validation of Seaside internal language
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Mastering Embedded Languages
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!" #"$%&
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change semantics
introduce new syntax
change syntax & semantics
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Adopt, Extend, Overload
Package Name
x = 1
y = 1 (2, 1)
(2, 2)(1, 2)
x = 2
y = 2
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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
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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
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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
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Homogeneous Tools
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Domain-Specific
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Traditional Smalltalk Compiler
Smalltalk
Parser
Semantic
Analysis
Bytecode
Generation
Executable
Code
Source
Code
Traditional Smalltalk Compiler
Smalltalk
Parser
Semantic
Analysis
Bytecode
Generation
Executable
Code
Source
Code
<parse> <transform> <attribute> <bytecode>
Rules
Traditional Smalltalk Compiler
Smalltalk
Parser
Semantic
Analysis
Bytecode
Generation
Executable
Code
Source
Code
<parse> <transform> <attribute> <bytecode>
Rules
<complete> <highlight>......
Traditional Smalltalk Compiler
Smalltalk
Parser
Semantic
Analysis
Bytecode
Generation
Executable
Code
Source
Code
<parse> <transform> <attribute> <bytecode>
Rules
Pidgin path
Creole path
<complete> <highlight>......
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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.
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BNFID ::= letter { letter | digit } ;
Ometa2id = letter (letter | digit)*
PetitParserid := #letter asParser ,! (#letter asParser / #digit asParser) star
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Smalltalk is a serious player in DSL
Trivial modelTrivial syntax
Internal DSLsEmbedded DSLsFull tool supportExtensible (build your own)Executable
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