Lab 8

Implement a small class hierarchy modeling objects as closures in GUCI3/4. The idea of this lab is to help you to understand the desugaring operation for objects by writing things down in the *un*-sugared form. That is, the forms you write for this lab will not use the syntactic sugar that you add for assignment 5.

• Start with your solution to assignment 3 OR 4.

• Add string values to your assignment.

• Add an expt binary operator, that accepts numbers a and b and computes a raised to the bth power. To make this easy, import the function of the same name from racket:

  (require (typed-in racket [expt : (number number -> number)]))

• Implement a Point in GUCI, as we’ve been doing in class. Include getter methods, and a "distance" function that accepts another point and returns the distance between this point and another point. Make sure your distance function works by writing tests in GUCI.

• Implement a Triangle class , that includes three points. Include a "perimiter" method that computes the perimiter of the triangle, using the Point class. As before, make sure to write test cases.

• Implement a Cons class, that represents a pair, including first and rest fields. Implement an Empty class, with no fields. Create examples of lists of numbers.

• Add getters called first and rest to the Cons class.] Develop the length method for Cons and Empty, that computes the length of a list.

• Starting here, you’ll need a working GUCI 4.

• Develop the doublemap method for Cons and Empty, that can be called on a list of numbers and returns a new list where every number is doubled. In order to make this work, you’ll need to make the constructor recursive, using the trick described in chapter 9 of the book.

• Add strings to your GUCI 4 language, and extend equality to handle strings (two strings are equal if they contain the same sequence of characters).

• Develop a interp method in GUCI 4, that accepts s-expression-like terms formed using numbers, strings, Cons, and Empty, and returns the number the term evaluates to. You should include addition, subtraction, multiplication and division in your mini-language. Note that there’s no need to separate parsing from evaluation in the mini-language.