CIS 22 - Data Structures

Part II - HTML Displayer v. 2

Overview

In Assignment #1, you created a simple HTML displayer. In this assignment you will use the Stack data structure to extend the displayer's functionality in two different ways. Of course, all the functionality from assignment 1 should still be present unless modified by this assignment. This assignment should be done in C++.

1. Improved Syntax Checking

In Assignment 1, your displayer only made some very simple checks on the syntax of the HTML files it was attempting to display. Use a Stack to implement checks for mismatched tags. For example, HTML such as

A new world from the ashes of the old

should be determined to be incorrect. (Of course, browsers are designed to minimize error messages, so most will display this in a way that may or may not have been intended by the author.) When your displayer detects such an error, it should display the page up to the point of the error, then issue an error message. This message should be as helpful as possible to an author who wants to correct the error. As in assignment 1, tags other than <A>, , and should not affect the display, even though your displayer will be analyzing the occurrence of these tags.

Several tags are not used as begin/end pairs, so your displayer should not give errors for those tags. In particular, your displayer should be "aware" of the , , <HR>, and <LI> tags.

Note that your displayer will only detect at most one such error per file.

2. The "Back" Button

In assignment 1, your user interface allowed the user 3 navigational choices: choose a link number, choose a file, or display the next page of the current file. For this assignment, use a Stack to implement the option of "going back" to previously displayed files. Your displayer should have a "memory" of at least the previous 10 files. If at any point it is not possible to go back ( because the earliest remembered page is being displayed), the "go back" option should not be offered to the user.

Extra Credit

Implement a "Forward" option, in a manner similar to the "Back" option. When it is not possible to go forward, the choice should not be offered to the user.

Testing

Your program must be thoroughly tested. An incomplete test will result in the assignment being returned for resubmission. You can only resubmit once-after that the assignment will no longer be accepted, so be sure you perform thorough tests the first time.

Your tests should include (but not be limited to) the following cases:

tags that are not closed (for example a without a ),
closing tags that do not match an opening tag,
improper nesting of tags,
going back one page,
going back several pages,
going back as many pages as possible.

You may have to run your program several times in order to test all cases.

What to Submit

I do not want to look at your output on the screen. Dump the screen output, print it and submit a hardcopy. Also submit all of your input source files. (You do not need to submit the files you downloaded from here.) Obviously, submit all the program and header files.

Annotate your submission by hand to indicate the various test cases. For example, write on the output "this shows what happens if a closing tag is missing"