added some notes
Exercise 3.33 - using the Constraint Propagation system
Exercises 3.34-35: new constraint squarer
Exercise 3.36: more frame analysis. is THIS the last one for the chapter??
Exercise 3.37 - code monkey see, code monkey do. ends this section with a whimper; much easier than Section 2.3. If conservation of difficulty holds between chapters, I have a BAD feeling about Setions 3.4 and 3.5...