This problem set continues the study of first class, abstract functions, and introduces generative recursion (Sect. 25).

--- Read each question carefully and follow the design recipe! It is also a good idea to read the surrounding text in HtDP so that you know what the question is really asking.

---

HtDP Problems: This may look short, but start early... it's actually a lot of work

21.1.1,
21.1.2: append and map are built in... call yours list-append and list-map
21.2.1: The question carries over to pg. 314
22.2.2: Use foldr here to define sort
26.1.1,
26.1.2: Be sure to follow the directions given...
27.2.4