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1. Add a new plug-in project de.cau.cs.rtprak.login.compiler to your workspace. Be sure to uncheck the option This plug-in will make contributions to the UI. Add dependencies to the two projects containing the Turing Machine metamodel and the programming language metamodel.
2. Add an Xtend Class to your project. The class should be placed in a subpackage where all the transformation code will go, such as de.cau.cs.rtprak.login.compiler.transform.
3. You will notice that your new class is marked with an error marker because of a missing dependency of the new plug-in project to org.eclipse.xtext.xbase.lib. If you hover over the error with your mouse, you can have Eclipse add all libraries required by Xtend to your project.

4. Define an entry method for the transformation that takes a TuringMachine instance as an argument and returns a Program. You can use the following definition as a starting point:

   Code Block
   language java
   /** * Transforms a given Turing Machine into an imperative program model. * * @param machine the Turing Machine to transform into an imperative * program. * @return a program model that implements the Turing Machine. */ def Program transformTuringToImperative(TuringMachine machine) { // Create the program we will transform the Turing Machine into val program = ImperativeFactory::eINSTANCE.createProgram() // TODO: Initialize program appropriately // TODO: Call methods that generate the Program model // Return the transformed program program }

   There's a few points to note here:

   
   
   • Lines in Xtend code don't have to and with a semicolon.
   • We have been explicit about the method's return type, but we could have easily omitted it, letting Xtend infer the return type.
   • The keyword val declares a constant, while var declares a variable. Try to make do with constants where possible.
   • The methods you call should be declared as def private since they are implementation details and shouldn't be called by other classes.
   • You may be tempted to add a few global variables that hold things like a global input variable or a pointer to the current state. While you could to that, def create methods might offer a better alternative...
5. Add code to transform the Turing Machine to an imperative program model. The imperative program metamodel contains enough stuff to implement Turing Machines.
6. Open the Plug-In Manifest Editor and switch to the Runtime tab. Add the package containing your transformation to the list of exported packages. (You may have to check the Show non-Java packages option in the Exported Packages dialog to see the package.)

Testing the Transformation

You will need a way to test the transformation, so we will have to make it available through the UI. Eclipse plug-ins often come with a separate UI plug-in that contains the UI contributions, with the base plug-in only offering the functionality itself. In our case, our base plug-in contains the transformation code, and the UI plug-in we will be creating next contains a menu contribution to make the transformation available.

1. Add a new plug-in project de.cau.cs.rtprak.login.compiler.ui to your workspace. This time, leave the option This plug-in will make contributions to the UI checked. Add dependencies to the two projects containing the Turing Machine metamodel and the programming language metamodel. Also add a dependency to our base plug-in that contains the transformation.
2. Add a menu contribution that is visible if a file containing a Turing Machine model is selected in the project explorer. The previous tutorial taught you how to add menu contributions.

3. Create a command handler that loads the turing machine model from the selected file, calls the transformation on the model, and saves the imperative program to a file with the same name, but different extension. You can use the following code as a template: (The code requires a dependency to com.google.inject to work.)

   Code Block
   language java
   @Override public Object execute(ExecutionEvent event) throws ExecutionException { ISelection selection = HandlerUtil.getCurrentSelection(event); if (selection instanceof IStructuredSelection) { Object element = ((IStructuredSelection) selection).getFirstElement(); if (element instanceof IFile) { IFile machineFile = (IFile) element; // Load Turing Machine TuringMachine machine = loadTuringMachine(machineFile); // Call the transformation Injector injector = Guice.createInjector(); TuringToImperativeTransformation transformation = injector.getInstance(TuringToImperativeTransformation.class); Program program = transformation.transformTuringToImperative(machine); // Save imperative program IPath programFilePath = machineFile.getParent().getFullPath().append( machineFile.getName() + ".imperative"); IFile programFile = machineFile.getParent().getFile(programFilePath); saveImperativeProgram(programFile, program); } } return null; } /** * Load the turing machine model from the given file. * * @param turingFile the file to load the turing machine model from. * @return the turing machine model. * @throws ExecutionException if the file couldn't be opened. */ private TuringMachine loadTuringMachine(IFile turingFile) throws ExecutionException { // TODO Implement. } /** * Saves the given imperative program in the given file. * * @param programFile the file to save the program to. * @param program the program to save. * @throws ExecutionException if there was an error saving the file. */ private void saveImperativeProgram(IFile programFile, Program program) throws ExecutionException { // TODO Implement }

Code Generation

TODO: Write this section.

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