SimJ Programming Language

1. SimJ Programming Language BUILD ON THE POLYGLOT COMPILER FRAMEWORK MIHAL BRUMBULLI 7th Workshop “SEERE” Montenegro-Risan 9-14 September 2007

2. Introduction • Goal: “Build a new programming language” • For beginners • Redable & Easy code • No complexity • Basic functionality (found in beginners programming text books) • For compiler design • Basic functionality (not too complex) • Most important data types • Very similiar to Java (not an exact copy of it) • Implemented in a compiler framework Polytechnic University of Tirana

3. Polyglot Compiler Framework • An extensible Java compiler toolkit designed for experimentation with new language extensions. • The base polyglot compiler is a mostly-complete Java front end. • It parses, performs semantic checking on Java source code and outputs Java source code. • Its power consists in doing so on other languages source codes. • The AST is translated into a Java AST and the existing code is output into a Java source file which can then be compiled with javac. Polytechnic University of Tirana

4. Framework Architecture Polytechnic University of Tirana

5. Language Extensions • An extension is a source-to-source compiler that accepts a program written in a language extension and translates it to Java source code. • The first step in compilation is parsing input source code to produce an AST. • Polyglot includes an extensible parser generator, PPG, which allows the implementer to define the syntax of the language extension as a set of changes to the base grammar for Java. Polytechnic University of Tirana

6. Language Extentions cont... • The second step consist in a set of passes that transform the produced AST in a JavaAST. • The pass scheduler selects passes to run over the AST of a single source file in an order defined by the extension. • Each compilation pass, if successful, rewrites the AST, producing a new AST that is the input to the next pass. • Finally, a Java compiler such as javac is invoked to compile the Java code to bytecode. Polytechnic University of Tirana

7. SimJ Language • Is a simplified version of the Java programming language. • Not just a reduced copy of Java (MiniJava). • Simple Java like program structure. • Not some simple, command like instructions (J0) . • Two possible targets: • Beginners with no experience in programming. • Compiler construction. Polytechnic University of Tirana

8. SimJ Language cont... • Classes, Methods, ... • Data types • boolean – true or false • int – integers • char – characters • string – sequence of characters • int[] – array of integers • Control flow • if else • for • while • switch Polytechnic University of Tirana

9. SimJ vs Java Java SimJ public class A { public static void main(String[] args) { try { BufferedReader reader = new BufferedReader(new InputStreamReader (System.in)); System.out.print(“Your name:”); String name = reader.readLine(); System.out.print(“\nHello, ”+name+ “!”); } catch (IOException ioexeption) { System.out.println(ioexeption); } } } class A { main() { print(“Your name:”); string name = readLine(); print(“\nHello, ”+name+“!”); } } Polytechnic University of Tirana

10. Implementation • The design process of SimJ includes the following tasks: • Syntactic differences between SimJ and Java are defined based on the Java grammar: • polyglot/ext/jl/parse/java12.cup. • Any new AST nodes that SimJ requires are defined based on the existing Java nodes found in: • polyglot.ast and polyglot.ext.jl.ast . • Semantic differences between SimJ and Java are defined. • Translation from SimJ to Java is defined. The translation produces a legal Java program that can be compiled by javac. Polytechnic University of Tirana

11. Implementation cont... • Resulting packages are: • ext.simj.ast • AST nodes specific to SimJ language. • ext.simj.extension • New extension and delegate objects specific to SimJ. • ext.simj.types • Type objects and typing judgments specific to SimJ. • ext.simj.visit • Visitors specific to SimJ. • ext.simj.parse • The parser and lexer for the SimJ language. Polytechnic University of Tirana

12. Conclusions • SimJ is a simple programming language that improves the learning of programming basic structures. • the existing approaches did not fully address the problem of a simplified Java like structured language and that is not only a reduced copy of it. • Simplicity of SimJ is principally gained by hiding some of the Java object-orientation syntax in the usage of basic statements. • This improves the understandability of the code, making it less confusing and definitely more easy to learn. Polytechnic University of Tirana

13. Conclusions cont... • Polyglot Framework is an effective and easy way to produce compilers for Java-like languages like SimJ. • It offers the possibility to generate a base skeleton for new language extensions on witch we can add the desired specifications. • SimJ is a simplified version of the Java programming language that is not only a reduced copy of it. • SimJ could be used by beginners that want to learn Java but don’t know anything about programming. • It is also a good choice for learning compiler design because of its well defined and easy to implement structure. Polytechnic University of Tirana

14. THANK YOU! Mihal brumbulli