stratego song zhou *include slides from language.org/stratego/slidesforsoftwaregeneration2001...
TRANSCRIPT
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: Rules: basic transformation steps Strategies: control application of rules
Stratego/XT Stratego 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 tree
Back End: GPP: a generic pretty-printer to emit the syntax tree
out Communication Language
Aterm: 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 Syntax
Problems Easy for computer to process Difficult for human being to read and
write Maybe to verbose to be specified
Solution Directly employ the concrete object
syntax to specify the rewriting rules in Stratego
Mix an Object Language With a Meta Language Object 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.
Example EvalPlus : |[ i + j ]| -> |[ k ]|
where <add>(i, j) => k TraceProcedure :
|[ function ~f(~* xs) = ~e ]| -> |[ function ~f(~* xs) = (print(~String(<conc-strings>(f," entry\\n"))); ~e; print(~String(<conc-strings>(f,"exit\\n"))))]|
Syntax Definition Formalism Both 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 Combination
The object language syntax definition can be imported into Stratego syntax definition
We also need define an additional combinationial syntax definiton, to specify the glues (quotation mark and antiquotaion mark)
Example of Combinational Syntax Definition
Theoretical Problems
Only 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-Explode Convert concrete
object syntax term into Stratego syntax term
Generic Definition of Meta-explode
Summarize
Rules rewriting Transformation strategy First-Class Pattern Matching Scoped Dynamic Rewrite Rules Concrete Object Syntax