[sanjoy]

Thank you for the comments. I agree with your caveat about the difficulty in applying the tools to software or programming. Although invariants are quite useful in programming too, and abstraction is an essential part of any large project. But I decided, perhaps wrongly, not to discuss the programming examples much. For example, an earlier draft had a discussion of abstraction and used the tree minilanguage that I wrote to make the tree diagrams, comparing the high-level abstractions it uses with the low-level lines of postscript or PDF code (near the bottom of the abstraction tower). But it ended up frightening lots of students, so I didn't include it in the published book.

-Sanjoy Mahajan