Changes

Summary

1. merged
2. clarified modules;
3. clarified signature;
4. more compact data;
5. minor performance tuning;
6. tuned signature;
7. more uniform treatment of properties (but < 0 should not occur here);
8. tuned signature;
9. clarified signature;
10. clarified signature;
11. misc tuning and clarification: more tight representation;
12. tuned: prefer "build" combinator;