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CS3 Fall 2005

CS3 Fall 2005. Lecture 11: Finish higher order functions Midterm Prep. Programming Style and Grading. During grading, we are going to start becoming “more strict” on style issues MiniProject #3 will be the start For the big project, style is important Why?

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CS3 Fall 2005

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  1. CS3 Fall 2005 Lecture 11: Finish higher order functions Midterm Prep

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

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

  4. Midterm 2 • Midterm 2: Nov. 14th (next Monday). • In the lecture slot plus 30 minutes (4-5:30 pm, 120 Latimer) • Practice exam in reader (do this all at once) • Check announcements for more practice items and solutions. • Review session • this Wednesday (Nov. 9), 7-9 p.m. • 306 Soda Hall (HP Auditorium).

  5. 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)

  6. 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

  7. 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

  8. Write successive-concatenation (sc '(a b c d e))  (a ab abc abcd abcde) (sc '(the big red barn))  (the thebig thebigred thebigredbarn) (define (sc sent) (accumulate (lambda ?? ) sent))

  9. 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)

  10. Chips and Drinks (snack 1 2)  3 • This includes (chip, drink, drink), (drink, chip, drink), and (drink, drink, chip). (snack 2 2)  6 • (c c d d), (c d c d), (c d d c)(d c c d), (d c d c), (d d c c) "I have some bags of chips and some drinks. How many different ways can I finish all of these snacks if I eat one at a time?

  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!

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