Parsing in K-framework

1. Parsing in K-framework Faculty of Computer Science University of AlexandruIoanCuza, Iași July 2, 2011 RaduMereuță Advisor: Prof. Dorel Lucanu

2. Outline • About K-framework • Kontributors • Short description • Functionality • Example • Contributions • The parsing technique • Problems • Solution • Conclusion

3. Kontributors • Joint work between Formal Systems Laboratory (FSL) from University of Illinois at Urbana-Champaign (UIUC) lead by Grigore Roșu and Formal Methods in Software Engineering (FMSE) from Al. I. Cuza University (UAIC) lead by Dorel Lucanu • UIUC team: Chucky Ellison, Patrick Meredith, Grigore Roșu, Traian Florin Șerbănuță, Andrei Ștefănescu, David Lazăr • UAIC team: Andrei Arusoaie, Irina Măriuca Asăvoae, Mihai Asăvoae, Gheorghe Grigoraș,Dorel Lucanu, Radu Mereuță, Elena Naum

4. K-framework • Started by Grigore Roșu in 2003 to teach programming languages • Define executable semantics of a programming language • Incorporates the advantages of classical approaches • Reduction semantics with evaluation contexts • Modular SOS (modularity) • CHAM (concurrency) • Accomplishments: • the complete C semantics (Chucky Ellison) • Java 1.4 (AzadehFarzan, Feng Chen, Jose Meseguer and Grigore Roșu) • Scheme (Patrick Meredith, Mark Hills, and Grigore Roșu) • Matching Logic (Elena Naum, GrigoreRoșu and Andrei Ștefănescu)

5. How Do They Do It? PDF Syntax(L) Latex PNG K Definition EPS Syntax(K) Pure K Maude Interpreter void main () { … } configuration <T> <k> $PGM </k> <env> .Map </env> <in> 1, 2, 3, … </in> <out> «  » </out> </T> Apply K rewrite rules

6. Example of K definition kmod SAMPLE is including BASIC syntax Exp ::= ID | INT | Exp "+" Exp | Exp "=" Exp syntaxStm ::= Exp ";" | StmStm configuration <T> <k> .K </k> <env> .Map </env> </T> rule [store]: <k> I=V => V:Int </k> <env> I:Id |-> _ => V </env> endkm !!! Problems

7. Search for a tool • Problems • Support for context-free space • Lexer ambiguities • No support for ambiguous grammars • Excluded: • ANTLR - LL • Gold Parser - LALR • LPG (JikesPG) - LALR • SDF - context-free

8. Syntax Definition Formalism • Originates from CWI in the Netherlands • Modular syntax definition formalism – easy to extend automatically • Scannerless Generalized Parser (JSGLR) • Entire context-free space • Declarative disambiguation filters { Exp "*" Exp -> Exp {left, cons("ExpMul")} Exp "/" Exp -> Exp {left, cons("ExpDiv")} Exp "%" Exp -> Exp {left, cons("ExpMod")} } > { Exp "+" Exp -> Exp {left, cons("ExpPlus")} Exp "-" Exp -> Exp {left, cons("ExpMinus")} }

9. Compilation overview • K definition = syntax (BNF) + semantic (rewrite rules) Syntax Semantics Anno(L) G1(L) Generate parser Disambiguation G1(D) Parser AST ASF Pure K G1(K) Parsing

10. Mixing two grammars K syntax Exp ::= ID | INT | Exp "+" Exp | Exp "=" Exp syntaxStm ::= Exp ";" | StmStm + subsorting to K + variables + in place rewriting + syntactic rejects Variable

11. Parsing problems rule <k> X </k> ... rule(cell("k", K(amb([ X:K, X:Id, Exp(X:Id), X:Int, Exp(X:Int), X:Exp, X:Stm, Id("X"), Exp(Id("X"))]) ), "k"))

12. Disambiguation • Extending the disambiguation filter • Eliminate anomalies • Collect configuration info - apply filter for cell types • Collect variables declarations - apply filter for variables • Remove extra subsortings • Infer the sort of the remaining variables

13. AST to Pure K • Disambiguated AST to Pure K • Pure K is the basis for the backend • Minimal syntax • definition using AST labels • Komputations • Cells • Data structures

14. Conclusion • Contributions • Finding a suitable parser • Developing a parsing technique • Disambiguation algorithm • Future work • Integration of the parser in K2.0 • Sort inference • Integration with Eclipse