Due: Wednesday, March 25, 2009 at 5:00 pm.
The goal of this problem set is to help you learn to design more complex class hierarchies and to use abstraction in an object-oriented language.
As always, you must follow the design recipe. The deliverables for the design recipe are as in the preceding problem set.
HtDC: 18.7-18.13, 18.16-18.18, 19.4
Layer 3 Layer 2 Layer 1 Layer 6 Layer 5 Layer 4 ----------------------------------------where the dotted line represents the bottom of the canvas. Your animation should support the "d", "a", and "q" commands, as in problem 2.4.
A Enumeration is either an OpenDotList or a ClosedDotList An OpenDotList is a list of Items A ClosedDotList is also a list of Items An Item is either a String or an Enumeration
Enumerations support the following operations:
Item get(int n) -- returns the n-th item in the enumeration (counting from 1). If there is no n-th item (either because n is greater than the length of the enumeration or because n is <= 0), returns the empty string.
Enumeration remove(int n) -- returns an enumeration like the original, except that the n-th item has been removed. If there is no n-th item, returns an enumeration just like the original.
Enumeration replace(int n, Item item) -- returns an enumeration like the this one, except that the n-th item (if any) is replaced by the given item.
Enumeration swap(int n, int m) -- returns an enumeration like the original, except that the n-th and m-th items are swapped. If there is no n-th or m-th item, returns an enumeration just like the original.
IListOfString render() -- as in homework problem 7.2, except that it
does not take a style argument: the style is determined by whether the
Enumeration is an OpenDotList or a ClosedDotList . Returns a list of
strings, as in 7.2. For example, the result of render might be an
object representing the following list of strings:
"* Here is the first item in a ClosedDotList, which we'll call list A" "* Here is the second item in the list." "* o The third item in the list is an OpenDotList, which we'll call list B" " o Here is the second item in the OpenDotList." " o o The third item in the OpenDotList is another OpenDotList, which we'll call list C" " o Here is the second item in list C." " o List C could have been a ClosedDotList, of course, but it wasn't." " o Here is the fourth, and last, item in list B." "* This is the fourth item in list A."
Every item that is a string should have exactly one open or closed dot in front of it, unless it occurs as the first item of a sublist, as in the case of lines 3 and 5 in the example above. [Puzzle: how many dots can a string have in front of it?]
Implement the class of Enumerations. Use abstraction to reduce the amount of duplicated code wherever feasible.
Last modified: Mon Mar 16 22:22:00 2009