PAPLJ in Xtext

An Xtext implementation of the PAPLJ language, a simplified Java dialect for teaching Programming And Programming Languages in Java.

Features

The PAPLJ project in Xtext has the following features:

• permissive grammar with operator precedence;
• core library;
• type checking;
• type inference;
• Java class generator.

Differences

The Xtext implementation of PAPLJ has some differences when compared to the Spoofax implementation. In the Xtext implementation:

• the syntax is a bit more permissive;
• keywords are not allowed in identifiers;
• casts are written as x as T instead of (T)x;
• null is assignable to everything;
• everything is assignable to Any;
• run is optional;

Build and Run

Import the nested existing PAPLJ projects into the workspace of Eclipse with the Xtext 2.11 installed in it.

Eclipse

To run an Eclipse instance with PAPLJ:

1. right-click the main project org.metaborg.paplj;
2. select Run As → Eclipse Application to launch the Eclipse instance;
3. in the new Eclipse instance, create a new Plug-in Project;
4. in the MANIFEST.MF, add org.metaborg.paplj to the Required Plug-ins dependencies;
5. in the src directory, create a new file ending with the .pj extension;
6. if asked, confirm the conversion to an Xtext project.

IntelliJ

To run an IntelliJ instance with PAPLJ:

Note: This doesn't currently work as no IntelliJ plugin has been released for Xtext 2.11.

1. open the Gradle Tasks view via Window → Show view → Other... → Gradle → Gradle Tasks;
2. expand the org.metaborg.paplj.parent project;
3. double-click the intellij idea/runIdea task to launch the IntelliJ instance;
4. create a new Java project - it doesn't need a JDK;
5. in the src directory, create a new file ending with the .pj extension.

Web Editor

To run the Web Editor with PAPLJ:

1. open the Gradle Tasks view via Window → Show view → Other... → Gradle → Gradle Tasks;
2. expand the org.metaborg.paplj.parent project;
3. double-click the run/jettyRun task to launch the Jetty server;
4. open the URL shown in the Console view.

Note: This doesn't load the PAPLJ core library.

Layout

The workspace consists of the following projects:

• org.metaborg.paplj.parent — Aggregator build so all modules can be built with one Maven command.
• org.metaborg.paplj — The grammar definition and all languge-specific components.
• org.metaborg.paplj.tests — Unit-tests for the language.
• org.metaborg.paplj.ide — Platform-independent IDE functionality.
• org.metaborg.paplj.idea — IntelliJ IDEA functionality.
• org.metaborg.paplj.ui — Eclipse functionality.
• org.metaborg.paplj.ui.tests — Eclipse unit-tests.
• org.metaborg.paplj.target — Eclipse target platform definition against which to build.
• org.metaborg.paplj.web — Web functionality.

Editing

Xtext Grammar

When changing the Xtext grammar, you need to regenerate the Xtext artifacts:

1. open the file Paplj.xtext in the org.metaborg.paplj package in the src directory of the org.metaborg.paplj project;
2. right-click the grammar editor;
3. select Run As → Generate Xtext Artifacts.

Guillemets

To get the guillemets used in Xtend files (that is, « and »), in the Eclipse editor press Ctrl+Shift+<, Ctrl+Shift+> (or on Mac Cmd instead of Ctrl).