Hello again, Kevin suggested:
Then you should have set the language to "Beginning Student" or "Beginning Student with List Abbreviations".
You're right. That makes the messages much better. I switched to 'Advanced' level because I thought that something was possibly not accepted because it was too difficult. My fault. Wolfgang asked:
[...logging facility in Helium...] Do you tell your students about the existence of this facility?
We certainly do. They don't seem to mind; I even feel that they think it's nice to help research.
I just have had a look at Helium and think that at least a deriving mechanism is absolutely needed.
There is 'show' function for each data type you write down. Eq and Ord are not generated but we will do that; we will need it anyway for our simple class system.
Furthermore, I think, the need to state equality functions explicitely as paramters of certain functions makes learning harder and not easier.
I don't know. Could be. We'll probably provide two different Preludes, one with and one without overloading. This would compare to the language levels in DrScheme. A lot is possible in this area.
But it's an interesting project. Keep going on it.
Don't worry. We just started... Cheers, Arjan