Programming Style and Grading

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 11th (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 10th, 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 • 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? • When you need the context (add-suffix '-is-great '(nate sam mary)) (nate-is-great sam-is-great mary-is-great) • 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!