The Xtend programming language comes with very nice documentation, which can be found on its website, http://www.eclipse.org/xtend. We will give an overview of Xtend in this chapter, but we strongly suggest that you then go through the Xtend documentation thoroughly. Xtend itself is implemented in Xtext and it is a proof of concept of how involved a language implemented in Xtext can be.
We will use Xtend throughout this book to write all parts of a DSL implementation. Namely, we will use it to customize UI features, to write tests, to implement constraint checks, and to write code generators or interpreters for all the example DSLs we will develop in this book. In particular, starting with version 2.4, all the stub classes generated by Xtext for your DSL projects are Xtend classes by default (instead of Java, as in the previous versions).
You can still generate Java stub classes by customizing the MWE2 workflow, but in this book we will always use Xtend classes. Xtend...
