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Exercise 3.1
Points and Rectangle **


The purpose of this exercise is to strengthen your understanding of functions used as classes in Scheme.

First, play with the existing Point class defined on this page available from the on-line version of this material.

As an example, construct two points and add them together. Also, construct two lists of each four points, and add them together pair by pair.

Define a new method in the Point class called (move dx dy), which displaces a point with dx units in the x direction and dy units in the y direction. We encourage you to make a functional solution in which move creates a new displaced point. (After that you may consider an imperative solution, in which the state of the receiving point can be changed with an assignment, set!).

Finally, define a new class, Rectangle, which aggregates two points to a representation of a rectangle. Define move and area methods in the new class.

As a practical remark to the 'class Point ' and the send primitive, be sure to define send before you define Point . (This is done to redefine an existing send procedure in MzScheme).


Solution