Description
This lab gives you practice in working with our implementation of the dslist class that mimics the STL
list class. Create a directory/folder named lab7 and download these files into that folder:
http://www.cs.rpi.edu/academics/courses/fall14/csci1200/labs/07_list_implementation/dslist.h
http://www.cs.rpi.edu/academics/courses/fall14/csci1200/labs/07_list_implementation/lab7.cpp
Checkpoint 1
The implementation of the dslist class is incomplete. In particular, the class is missing the destroy_list
private member function that is used by the destructor and the clear member function. The provided test
case in lab7.cpp works “fine”, so what’s the problem?
Before we fix the problem, let’s use Dr. Memory and/or Valgrind to look at the details more carefully.
You should use the memory debugging tools both on your local machine and by submitting the files to
the homework server (we have set up a practice space for Lab 7). Study the memory debugger output
carefully. The output should match your understanding of the problems caused by the missing destroy_list
implementation. Ask a TA if you have any questions.
Now write and debug the destroy_list function and then re-run the memory debugger (both locally and
on the submission server) to show that the memory problems have been fixed.
To complete this checkpoint, show a TA the implementation and memory debugger output before and
after writing destroy_list.
Checkpoint 2
One subtle difference between the STL list implementation and our version of the dslist class is the
behavior of the iterator that represents the end of the list (the value returned by end()). In STL you may
decrement the end iterator. For example, you can print the contents of a list in reverse order:
std::list::iterator itr = my_lst.end();
while (itr != my_lst.begin()) {
itr–;
cout << *itr;
}
The syntax is admittedly rather awkward, that’s why we would typically rely on reverse iterators to do this
task. How does the dslist class behave on a corresponding test case? Try it out. How could you fix the
implementation so that it more closely matches the behavior of the STL version? There are a couple different
options… If you can’t come up with one quickly, please raise your hand and ask a TA. Make the necessary
changes to the implementation and test out your solution.
To complete this checkpoint, describe to a TA how you changed the implementation to allow the end
iterator to be decremented.
