JastAdd Tutorial Examples

 

PicoJava

This example shows how to implement semantic analysis for an object-oriented language with inheritance and nesting. Features illustrated include abstract syntax trees, reference attributes, broadcasting, parameterized attributes, context-dependent rewrites, circular attributes, imperative aspects, and connection to parser.

While the PicoJava language is small, the example shows off the main features in JastAdd and their typical use. It illustrates how quite complex problems can be solved in a simple way. E.g., how to implement name resolution in the presence of both inheritance and nesting; how to deal with qualified names and their types; how to check assignments in the presence of hierarchical types; and how to use the Null pattern to deal with erroneous programs.

The solutions used in PicoJava are typical for how JastAdd is used, so we recommend studying this example before looking at real projects like the Extensible Java Compiler.

DevirtualizationAnalyzer

The DevirtualizationAnalyzer component is an extension of the Java1.4Frontend that implements a whole-program analysis of which method calls can be devirtualized. The example illustrates how advanced analyses can be implemented in a simple way on top of an existing compiler component. The implementation is currently in an experimental stage, not yet taking all of Java's langauge constructs into account.

 

Metrics

The Metrics component is an extension of the Java1.4Frontend that computes a set of object-oriented metrics proposed by Chidamber and Kemerer. These metrics include structural properties such as the height of inheritance tree and number of subclasses, but also more global properties such as the analysis of coupling between classes. Internal properties such as the lack of cohesion of methods within a class and the number of weighted methods per class are also computed.

 

Non-Null Types for Java

Non-null types is a type-based approach to detect possible null pointer violations in code statically at compile time. We have extended a Java compiler, in a modular way, to include non-null types. This is an example of how a large JastAdd project can be extended in an easy and declarative way. We have also implemented an inference algorithm to retrofit legacy code to include non-null types.

 

JavaDemoNames - Modular name analysis for Java using JastAdd

We show how Java name analysis including ambiguities related to names of variables, fields, and packages, can be implemented in a declarative and modular manner using the JastAdd compiler construction system. The example defines a tiny subset of Java that demonstrates all challenges in Java name analysis. The same technique has been used in the JastAdd Extensible Java Compiler

Context-free Grammar

This example shows how circular attributes can be used for doing a static analysis of context-free grammars, computing the Nullable property and the First and Follow symbols for nonterminals in the grammar. The example provides a nice illustration of the use of several circular attributes.

Knuth's Binary Numbers

This example shows how to use JastAdd to implement Knuth's seminal example from 1968 where the values of binary numbers are defined using attribute grammars. The example illustrates simple use of synthesized and inherited attributes. No parser is included. The test ASTs are built explicitly in Java code.

This example is very small and simple. It is particularly intended for people already familiar with conventional attribute grammars, and who would like to see what this well-known example looks like in JastAdd. Note that this example does not at all show the full potential of JastAdd since it only illustrates the simple features of synthesized and inherited attributes.

HelloWorld On JavaCC

This is a very small "hello world"-like example showing how you can build a JastAdd project on top of the parser generator JavaCC and JJTree (rather than on jflex and beaver). The example also illustrates a simple imperative aspect.