Is there a way to add comments?
a. Comments in the Projectional Editor of the Concepts/constrains/etc.
• For documentation / explanation
• For commenting out some "code" during development
b. Comments which will appear in the sandbox Node?
• For guiding the user
Answer (by Vaclav Pech):
In language definition languages comments are allowed only in a few places, e.g. to describe actions, key maps or action maps and are typically labelled as “description". You can comment out snippets of BaseLanguage code inside blocks of BaseLanguage code (concept functions), just like you would in any Java methods, but you cannot comment out a whole action-map entry, for example. This is currently not supported, I’m afraid.
If your languages should support comments in user code, you need to explicitly add support for this into your languages. See https://confluence.jetbrains.com/display/MPSD32/Documentation+comments