This assignment is due on Sunday, February 5 at 11:59pm. Submit it using Handin as assignment lecture9. You only need to submit the first 6 exercises.
Read every word of instructions. If a problem asks you to define a constant, don’t define a function instead. If a problem tells you to design a function with a certain name, don’t use a different name. If a problem says your function should return a traffic light, don’t make it return an image.
Define everything you use. If your signature refers to a type of data, give its data definition. If your code uses a courtesy function, give its structure definition. You don’t need to repeat a definition in the same file or on the same exam.
Solve old problems. A great way to review is to solve old problems in lectures, labs, and problem sets. Exam problems will be similar. When you practice programming on a computer, run your program as often as you can, and try out the Stepper. When you practice programming on paper, predict what happens during testing, and work out step-by-step calculations.
Students who practice thoroughly with old problems are often surprised by how well they do on the midterm.
; A Point is (make-point Number Number) (define-struct point [x y]) ; A Person is (make-person String Number) (define-struct person [name age]) ; A TrafficLight is one of: ; - "red" ; - "yellow" ; - "green"
; Exercise 1 ; 17 is a Number ; true is a ??? ; "true" is a ??? ; "red" is a ??? ; (circle 10 "solid" "red") is a ??? ; (make-point 3 4) is a Point ; (make-person "Dan" 22) is a ???
3 big-bang with structures
“The ontology of objects is a specifically Western construct… The object is what can be handled, manipulated, constructed, built up and broken down, with clear accountability of matter gained and lost.” —
Iris Marion Young
Exercise 4. Design the function half-point, which takes a Point and produces a new Point where the coordinates are half as big. Show step-by-step calculations for one of your function examples.
Exercise 5. Design the function initial, which takes a Person and produces a string which is the first letter of their name. The substring function will be helpful. Show step-by-step calculations for one of your function examples.
Exercise 6. Develop a data and structure definition for a Triple, which holds three numbers. Design a function average-triple which takes a Triple and produces the average of its three numbers. Then design a function normalize-triple which takes a Triple and subtracts the average of its three numbers from each of its three numbers, producing a new Triple. For example, normalizing the triple 5 2 2 should produce the triple 2 −1 −1.
For the rest of this page, you don’t need to submit anything, but do try the exercises anyway. We’ll work through the material together in class.
It’s easy to confuse an enumeration and a structure. Below is a side-by-side comparison.
; A PumpkinPie is (make-pie Crust Filling ToastedPecans) (define-struct pie [crust filling toasted-pecans]) ; A Crust is (make-crust Dough Boolean) (define-struct crust [dough egg-wash]) ; A Dough is one of: ; - "Claire's rye" ; - "Brad's AP flour" ; A Filling is one of: ; - "Libby" ; - "Brad, Claire and Libby" ; A ToastedPecans is one of: ; - "butter + sugar" ; - "sugar + egg whites"