[plt-scheme] htdp and modules

Matthias Felleisen wrote:

> If I were to include modules in teaching languages, what I sketched out 
> with my messages to Jan is what I would include. So this is a strange 
> issue: the module stuff is almost orthogonal to the language level. Due 
> to restrictions on where function names can appear, you can't use 
> Beginning Student [+ ...] but that's okay with me.

That is just fine.

To talk about ADTs, we also need the ability to optionally make 
structures opaque outside a module, without hinting at deep magic. Also 
some way of letting students run non-blackbox tests without having to 
know I/O -- perhaps the ability to "run" a module and evaluate/print the 
expressions in it. --PR