Xtext is an excellent framework for creating textual languages together with a rich editing environment. One of the exciting new features of the upcoming Xtext 2.0 is the integration of the general purpose expression language Xbase. A good way to explore a new language is via an interactive programming environment (often called a REPL for Read-Evaluate-Print-Loop). So far Xtext only provides an interpreter for Xbase, without an actual REPL. The goal of Xrepl is to provide an interactive console for languages that are based on Xbase. Of course, the Xrepl will support all the goodness provided by Xtext, such as syntax highlighting, code completion, and validation. Xrepl is currently work in progress and will be released after Xtext 2.0. If you want to try Xrepl, there is a beta version available that works with the current Xtext 2.0M5 milestone.
Update site: http://xrepl.org/updatesite/milestones/
Source code: https://github.com/sebastianbenz/xrepl