This is a second part of the Calculator Language Tutorial covering constraints and type-system. You might also want to view the first part.
This screncast provides an alternative way to learn MPS. Folowing the steps described in the on-line introductory MPS Tutorial the screencast will guide you through the process of creating scoping constraints and simple type-system rules for the Calculator Language we built in the first part.
If you find the on-line tutorial a bit dry and difficult to follow, this screencast may help you get over it. Try it out!