Katja Laboratory Abstract Syntax Trees in Java with Katja

Transcription

1 Katja Laboratory Abstract Syntax Trees in Java with Katja Lecture Compiler and Language Processing Tools 2011 Jan Schäfer (slides by Jean-Marie Gaillourdet) Software Technology Group TU Kaiserslautern c Software Technology Group, TU KL Katja Lab 1

2 Introduction What s Katja? code generator for order-sorted datatypes in Java (and Haskell and Isabelle/HOL) goal: simplify generation and handling of ASTs in Java enable the implementation of attribute grammar systems (not quite yet) c Software Technology Group, TU KL Katja Lab 2

3 Design decisions Introduction functional terms in Java immutable globally shared strutcural equality implies reference equality declarative specification as order-sorted datatypes statically typed (as far as possible) c Software Technology Group, TU KL Katja Lab 3

4 Introduction Katja - The Command Line Tool Executing Katja java -jar katja.jar -b java -o -j spec.katja Input: Specification of order-sorted datatype (*.katja) Output: SpecificationName.jar Generated sources and class files katja-common.jar (only with -j) Base library of Katja c Software Technology Group, TU KL Katja Lab 4

5 Katja Specifications Introduction specification Formulas external Integer external String Formula ( Expression top ) Expression = False Implies Not Predicate False ( ) Implies ( Expression left, Expression right ) Not ( Expression expr ) Predicate ( String name, Parameters vars ) Parameters * Variable Variable ( Integer index ) c Software Technology Group, TU KL Katja Lab 5

6 Introduction Katja Specifications With Syntactic Sugar specification Formulas external Integer external String Formula ( Expression top ) Expression = False ( ) Implies ( Expression left, Expression right ) Not ( Expression expr ) Predicate ( String name, Parameters vars ) Parameters * Variable Variable ( Integer index ) c Software Technology Group, TU KL Katja Lab 6

7 Katja Terms Introduction Formula top() Not expr() Predicate name() vars() "P" Parameters get(0) get(1) get(2) Variable Variable Variable index() index() index() c Software Technology Group, TU KL Katja Lab 7

8 Introduction What is generated? an interface per sort a specification class with static constructor methods hidden implementations and utility classes/interfaces Example import static softech.formula.formulas.*; import softech.formula.*;... { Formula f = Formula( Not( Predicate( "P", Parameters( Variable(17), Variable(4), Variable(42))))); } c Software Technology Group, TU KL Katja Lab 8

9 Last missing part Introduction specification Formulas backend java { package softech.formulas import java.lang.string import java.lang.integer } external String external Integer... c Software Technology Group, TU KL Katja Lab 9

10 Expressions Abstract Datatype aka. Terms Literal ( Integer value ) Variable ( String name ) Plus ( Expression left, Expression right ) Minus ( Expression left, Expression right ) Mult ( Expression left, Expression right ) Div ( Expression left, Expression right ) Expression = Plus Minus Mult Div Literal Variable c Software Technology Group, TU KL Katja Lab 10

11 Switch Classes Abstract Datatype aka. Terms simulate switch construct of Java over variants... f.top().switch( new Expression.Switch<Integer,NE> { public CaseFalse() throws NE {... } public CaseImplies(Expression left, Expression right) throws NE {... } public CaseNot(Expression expr) throws NE {... } public CasePredicate(String name, Parameters vars) throws NE {... } }); c Software Technology Group, TU KL Katja Lab 11

12 Abstract Datatype aka. Terms Task 1 create a Katja specification file for expressions compile it write a method Integer eval(expression e) to evaluate expressions without variables use an exception to signal the presence of variables c Software Technology Group, TU KL Katja Lab 12

13 Solution Abstract Datatype aka. Terms c Software Technology Group, TU KL Katja Lab 13

14 Context-dependent Terms aka. Term-Positions Terms vs. Term-Positions FormulaPos term() Formula parent() top() NotPos term() top() Not parent() expr() expr() parent() PredicatePos name() vars() Predicate name() vars() StringPos ParametersPos "P" Parameters get(0) get(1) get(2) get(0) get(1) get(2) VariablePos VariablePos VariablePos Variable Variable Variable index() index() index() index() index() index() IntegerPos IntegerPos IntegerPos term() root Formula Pos c Software Technology Group, TU KL Katja Lab 14

15 Context-dependent Terms aka. Term-Positions What is generated? a term position interface per sort hidden implementations one addition constructor method (FormulaPos) default visitor common super-type (softech.formula.formulas.sortpos) c Software Technology Group, TU KL Katja Lab 15

16 Visitors Context-dependent Terms aka. Term-Positions interface FormulaPos... { class DefaultVisitor... { void visitformulapos(formulapos term) {... } void visitnotpos(notpos term) {... } void visitimpliespos(impliespos term) {... }... } } c Software Technology Group, TU KL Katja Lab 16

17 Context-dependent Terms aka. Term-Positions Task 2 implement a PrettyPrinter based on the DefaultVisitor decide whether to print out parenthesis based on the parent c Software Technology Group, TU KL Katja Lab 17

18 Solution Context-dependent Terms aka. Term-Positions c Software Technology Group, TU KL Katja Lab 18

19 Context-dependent Terms aka. Term-Positions Modifying Term Positions every term position can be replaced by a term of equivalent sort immutable! KatjaSort<R> replace(object o) sometimes you have to use.cast() c Software Technology Group, TU KL Katja Lab 19

20 Context-dependent Terms aka. Term-Positions Post- and Preorder every position has a preorder() method, which goes to the next position in pre order every position has postorder and postorderstart methods c Software Technology Group, TU KL Katja Lab 20

21 Context-dependent Terms aka. Term-Positions Task 3 implement a method simplify which simplifies constant expressions to constants use a post order path through the positions c Software Technology Group, TU KL Katja Lab 21