Stratego. Song Zhou *Include slides from http://www.stratego-language.org/Stratego/SlidesForSoftwareGeneration2001. Introduction. Stratego is “ a language for the specification of transformation systems based on the paradigm of program rewriting strategies ” . Basic components: - PowerPoint PPT Presentation
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StrategoSong Zhou
*Include slides from
http://www.stratego-language.org/Stratego/SlidesForSoftwareGeneration2001
IntroductionStratego is a language for the specification of
transformation systems based on the paradigm of program rewriting
strategies.Basic components:Rules: basic transformation
stepsStrategies: control application of rules
Stratego/XTStratego is only a term-rewriting language. Term in,
Term out. XT can combine Stratego with other tools to create a
transformation system.Front End: SGLR: a generic parser creating
syntax treeBack End:GPP: a generic pretty-printer to emit the
syntax tree outCommunication LanguageAterm: a term exchange
format
Transformation Rules
Outline
Transformation Strategies
Traversal
First-Class Pattern Matching
Scoped Dynamic Rewrite Rules
Concrete Object Syntax
What is wrong with Abstract SyntaxProblemsEasy for computer to
processDifficult for human being to read and writeMaybe to verbose
to be specifiedSolutionDirectly employ the concrete object syntax
to specify the rewriting rules in Stratego
Mix an Object Language With a Meta LanguageObject Language
inside Meta Language: Extending Meta Language with a quotation
operator that lets the meta-programmer indicate object language
fragments. Meta Language inside Object Language:Antiquotation
allows the use of meta-programming language constructs in these
object language fragments to splice meta-computed object code into
a fragment. If Meta Language equals Object Language then the syntax
extension is easy by just adding quote and antiquote operators to
Meta Language.
ExampleEvalPlus : |[ i + j ]| -> |[ k ]| where (i, j) =>
kTraceProcedure : |[ function ~f(~* xs) = ~e ]| -> |[ function
~f(~* xs) = (print(~String((f," entry\\n"))); ~e;
print(~String((f,"exit\\n"))))]|
Syntax Definition FormalismBoth the Stratego syntax and the
object language syntax is specified using the Syntax Definition
Formalism (SDF)An SDF production sym1 ... symn -> sym declares
that an expression of sort sym can be constructed by the
concatenation of expressions of sorts sym1 to symn.SDF supports
regular expression operators such as {Exp ";"}*, which denotes a
list of Expressions separated by ; semicolons. SDF integrates the
definition of lexical and context-free syntax in one formalism. The
formalism is modular the syntax definition of a language can be
divided into smaller (reusable) modules syntax definitions for
separate languages can easily be combined.
Stratego Syntax Definition in SDF
Tiger Syntax Definition in SDF
Corresponding Abstract SyntaxSignature
Syntax CombinationThe object language syntax definition can be
imported into Stratego syntax definitionWe also need define an
additional combinationial syntax definiton, to specify the glues
(quotation mark and antiquotaion mark)
Example of Combinational Syntax Definition
Theoretical ProblemsOnly full class of CFG have closure
property. LL, LR and other subclasses of CFG are not closed under
composition.SDF2 supports scannerless generalized-LR parsing
Meta-ExplodeConvert concrete object syntax term into Stratego
syntax term
