2. Feb 28More complicated recursions March 7Tree recursion, etc. Number-spelling Miniproject (#2) March 14Higher order procedures March 21Spring Break March 28Tic-Tac-Toe – read SS chapter 10! Case Study: Making Change (tree-recursion) April 4Elections mini-project (#3) April 11Midterm #2 (during lecture) Extending sentences, words to lists (in lab) April 18Advanced list processing (recursion) Start on the big project April 25 and on… Work on the big project (check-off 1, 2)

3. Programming Style and Grading During grading, we are going to start becoming “more strict” on style issues –Starting with miniproject #3 –For the big project, style is important Why? –Program maintenance: 6 months later, will you know what your code does? –Code “literacy”: sharing code

4. What issues of style matter? Avoid nesting conditional statements Keep procedures small ! Good names for procedures and parameters Adequate comments –Above and within procedures Put tests cases in a comment block Indent to aid program comprehension

5. Midterm 2 Midterm 2: April 11 th (next Monday). –In the lecture slot (5-6 pm, 105 North Gate) –Practice exam in reader (do this all at once) –Check announcements for more practice items and solutions. Review session this Sunday, April 10 th, 10-12. 430 Soda (Wozniak lounge). –Email problem requests to Fu, Elham, and Nate.

6. What does midterm #2 cover? –Advanced recursion (accumulating, multiple arguments, etc.) –All of higher order functions –Those "big" homeworks (bowling, compress, and occurs-in) –Elections miniproject –Reading and programs: Change making, Difference between dates #3 (HOF), tic-tac-toe –SS chapters 14, 15, 7, 8, 9, 10 –Everything before the first Midterm (although, this won't be the focus of a question

7. make-decreasing –Takes a sentence of numbers –Returns a sentence of numbers, having removed elements of the input that were not larger than all numbers to the right of them. (make-decreasing '(9 6 7 4 6 2 3 1))  (9 7 6 3 1) (make-decreasing '(3))  (3)

8. When do you NEED lambda? 1.When you need the context (add-suffix '-is-great '(nate sam mary))  (nate-is-great sam-is-great mary-is-great) 2.When you need to make a function on the fly

9. Procedures that make procedures Generally, name procedures that create procedures "make-XXX" (make-bookends 'o)  #[closure arglist=(inner-wd) d7d0e0] ((make-bookends 'o) 'hi)  ohio ((make-bookends 'to) 'ron)  toronto (define tom-bookend (make-bookends 'tom)) (tom-bookends "")  tomtom

10. Repeated (this is hard) > (repeated butfirst 3)  #[closure arglist=(x) d81d70] > ((repeated butfirst 3) '(a b c d e f g))  (d e f g) > ((repeated butlast 3) '(a b c d e f g))  (a b c d) What does the function that (repeated butfirst 3) returns look like? Write repeated

11. Lists (after the midterm) Lists are containers, like sentences where each element can be anything –Including, another list ((beatles 4) (beck 1) ((everly brothers) 2) … ) ((california 55) (florida 23) ((new york) 45) ) (#f #t #t #f #f …)

12. List constructors cons –Takes an element and a list –Returns a list with the element at the front, and the list contents trailing Append –Takes two lists –Returns a list with the element of each lists put together List –Takes any number of elements –Returns the list with those elements

13. List selectors car –Like first cdr –Like butfirst

14. Common list procedures Map = every Filter = keep Reduce = accumulate Null? = empty? Recursion is just the same!