Assignment 2 Stacks (with Templates and Exception)


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CMPT 225 D2

Assignment 2
Stacks (with Templates and Exception)
You are to write a generic (templated) C++ Stack class, along with some other code mainly for testing
the Stack implementation.
The principal class will be called Stack, and it should be templated on the type of the stack. (E.g.
Stack<int> or Stack<string>.)
Stack has the following member functions (T is the template parameter).
type name
T& pop() // returns and removes the top of the stack.
// (Or throws an EmptyStackException if the stack is empty)
void push(T&) // pushes the argument onto the stack.
bool empty() // returns true if the stack is empty.
int size() // returns the number of elements in the stack.
int capacity() // returns the current capacity of the stack.
It should also have a constructor and a destructor. As a constructor argument, it should take a capacity,
which is the size of the array that it makes to hold the stack elements. This argument should default to
4. If there is a push() operation and the stack is at capacity (i.e. it’s full), then make a new array that has
twice the size of the old capacity and copy the elements from the old array to the new array. Delete the
old array.
EmptyStackException is a new class that you should create. It can be created in the same file as the
Stack class.
To exercise your stack functionality, create a class called ArrayUtils, and give it a single member
function, reverse(), which is static. Its arguments should be an array and its size. It should be
templated so as to be able to take any array. Reverse should reverse the array that it is passed by (1)
making a stack of that type, (2) pushing each element of the array on the stack, and (3) popping each
element of the array from the stack, placing it in the correct place in the array. It should return its array
Your main routine should call several test functions. These are: testStackUnderflow(),
testStackGrowth(), testReverseIntegers(), testReverseStrings(), and testReverseEmployees().
testStackUnderflow() will check to see if your exception is thrown when a stack underflows. In it, you
should use a try-catch statement that catches EmptyStackException. Inside the try block, create a Stack,
push an element onto it, pop it twice, and then print “did not catch exception”. The second pop should
cause an exception; if this is properly done, then the line that prints “did not catch exception” should
not execute. Inside the catch block, print “caught EmptyStackException”.
testStackGrowth() will check to see that your stack grows as appropriate. In it, create a stack with
capacity 4. Push items onto it, printing them as you push. After 5 items, print the capacity of the stack.
Keep pushing and printing items until you get 9 items, and print the capacity of the stack again. Then
pop all of the elements, printing them as you do so.
The remainder of the test functions are relatively the same and are for testing out that you did the
templating correctly. In testReverseIntegers(), make an array of 12 integers, print it, call reverse (in
ArrayUtils) on it, and print it again. In testReverseStrings(), make an array of 12 strings, print it, call
reverse on it, and print it again. In testReverseEmployees(), make an array of 12 Employees, print it, call
reverse on it, and print it again.
You’ll have to make a class Employee for the last test. This class should have two constructor
arguments, which are a name and an employee ID number. The class should be immutable with getters
for the name and ID number. It should also have a function toString() which returns a string that is the
name followed by a space followed by the ID number. Use this function in printing an Employee in
Print a blank line between each pair of tests in main.
All classes should be in separate files (.cpp and/or .h) named with the class name. (The exception class
is an exception to this.)
You will be judged on correctness of your code and on code style, so don’t forget to keep your code
clean as you develop it! (Or at the very least, clean it up before submission. We don’t want to see
untidy code.)
note: Tests that print results, like the ones above, are in general discouraged in software engineering.
Why? Because we do so many tests of our classes and functions that a human quickly becomes fatigued
if they have to look at all the test output. The tests here are nowhere near the amount of tests that one
would in practice write to ensure the correct operation of Stack. Tests are now normally made to be
silent (no printing) if they succeed, and only print something if they fail. If we were to do this for, say,
testReverseIntegers(), we’d have to test that the array we got back from reverse() contained the reverse
elements from what we sent in to the function. (We’d check to make sure that each element of the
resulting array was correct.) Do not do this for this assignment. We will expect your code to print
results as described above.
more fun (not required)
If you finish the above and want to have more fun (but no extra credit), implement a templated
StackDuo class. This class contains two stacks A and B of the templated type. It has operations push,
which pushes an item onto stack A; transfer, which pops an item from stack A and puts it on stack B;
pop, which pops and returns an item from stack B; size, which is the sum of the number of elements in
the two stacks; and sizeA and sizeB, which return the number of elements in stack A or stack B
respectively. Figure out their argument and return types.
Now add a function to main which tests the StackDuo. You may have to do several tests, but try to
make the results easy to interpret. You may want to test its exception-throwing behaviour as well.
Do not turn in your StackDuo code. We will not look at it. You can ensure that it is correct by testing it.
(advanced!) As a theoretical exercise, consider a sequence of n pushes, n transfers, and n pops, with
these operations intermingled. Suppose the pushes are of consecutive integers 1, 2, 3, …, n. Record
the number sequence that you get from the pops. Can you get every permutation of 1, 2, 3, …, n out of
the StackDuo by some sequence of operations? If not, which permutations can you get?
For instance, suppose n is 4 and we want the permutation 1423.
We could:
pop() // 1 is popped.
transfer() // leave 2 on stack B
push(3) // leave 3 on stack A
pop() // 4 is popped.
pop() // 2 is popped.
transfer() // 3 is moved from A to B
pop() // 3 is popped.

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