JastAdd2

JastAdd2 was developed at Lund University by Torbjörn Ekman, Görel Hedin, and Eva Magnusson. JastAdd2 has recieved additional contributions from Emma Söderberg, Jesper Öqvist and Niklas Fors.

For additional contributors, see the change logs.

License

JastAdd2 is covered by the modified BSD License. For the full license text see the LICENSE file.

Obtaining JastAdd2

The latest version of JastAdd2 can be found at jastadd.org.

Dependencies

JastAdd2 requires a Java Runtime Environment (JRE) to run, and a JDK to build. The minimum required Java version for JastAdd2 is Java SE 6.

JastAdd2 uses JavaCC, JJTree, and Apache Ant. JavaCC and JJTree are included in the source tree of JastAdd2, so the only external tools needed are Java and Ant. See licenses/javacc-BSD for the full license text.

The context-free grammar used in JastAdd is based on an example from JavaCC.

The README file for the binary distribution (README-binary-dist.md) is written in the markup language Markdown. This file is converted to HTML using a Python script during the build script. The Python script requires the Python-Markdown package for Python. The Python-Markdown package can be installed using pip install markdown.

Building

Builds are done by using the Apache Ant script build.xml:

Ordinary build (generate and compile):
```
> ant
```
Create a new jar file (jastadd2.jar)
```
> ant jar
```
Make a new release (builds jar file, source- and binary zip files):
```
> ant release
```
Delete generated files
```
> ant clean
```
Bootstrap jastadd2 (replace the jastadd2.jar used to build jastadd2). For stability, bootstrap is done seldom and only with extra testing.
```
> ant bootstrap
```

File Types

.ast JastAdd abstract syntax tree files
.jrag JastAdd semantics files. Usually declarative.
.jadd JastAdd semantics files. Usually imperative.
.java Regular Java sources
.jjt JavaCC files, using the JJTree AST-building commands.

Directory Structure

src/java Java source files
- src/java/jastadd/
  - JastAdd.java The main class. Compiles the .ast and .jrag files to Java files.
  - JastAdd.jrag Extends the top AST node (Grammar) with methods for adding .ast and .jrag info.
  - CommandLineArguments.java A general class for reading in args and options from the command line.
  - JastAddTask.java Implements an ANT task for running jastadd, including support for various args and options.
src/jastadd/ JastAdd aspect and AST specifications
src/javacc/ JavaCC files
src/res/ Templates, property files and other resources that are included in the JastAdd jar file.
- src/res/template/ Template root
src/gen/ Generated source files
doc Documentation html files.
- reference-manual.html The reference manual
- release-notes.html The release nodes
- index.html For download from the web
- *.php Helper files for browsing uploaded files on the web
tools 3rd party jar files used to build build JastAdd
README.md This file.
LICENSE Text file with the jastadd LICENSE.
release.sh A script printing the commands for doing a release.
ChangeLog A textfile recording changes done to JastAdd, intended for users of JastAdd (focusing on external behavior).
ChangeLogUntil2010.txt A textfile containing cvs log messages until 2010 when the system was moved to svn.

Understanding the Implementation

Overall behavior when running JastAdd:

First, options are read and global flags are set.
Then, an incomplete AST is built by parsing the .ast file.
Then, the .jrag files are parsed, and their information is weaved into the AST.
Now, the AST is complete, and attributes can be accessed.
Then, possible errors are printed.
Then, target AST classes are generated.

Parsing

JavaCC and its tree-building extension, JJTree, are used for parsing. They assume top classes called Node and SimpleNode. Normally, JJTree generates its own AST node subclasses, but we "fool" it to use the AST classes generated by JastAdd instead (by generating them before we run JavaCC/JJTree).

However, we let JJTree generate the AST classes for the Java code used inside equations in .jrag files. This is because these expressions are not analyzed by JastAdd. They are just unparsed at appropriate places in the generated Java code.