Why is my print function spitting out garbage and my current function not working properly?

Question

heres the header file http://pastebin.com/g0z7LkeN heres the implementation file http://pastebin.com/USHbjbYC

and here is the test debugger file (not supposed to change it)

// FILE: sequence_test.cpp
// An interactive test program for the new sequence class
#include <cctype>       // Provides toupper
#include <iostream>     // Provides cout and cin
#include <cstdlib>      // Provides EXIT_SUCCESS
#include "sequence2.h"  // With value_type defined as double
using namespace std;
using namespace CISP430_A2;

// PROTOTYPES for functions used by this test program:
void print_menu( );
// Postcondition: A menu of choices for this program has been written to cout.

char get_user_command( );
// Postcondition: The user has been prompted to enter a one character command.
// The next character has been read (skipping blanks and newline characters), 
// and this character has been returned.

void show_sequence(sequence display);
// Postcondition: The items on display have been printed to cout (one per line).

double get_number( );
// Postcondition: The user has been prompted to enter a real number. The
// number has been read, echoed to the screen, and returned by the function.


int main( )
{
    sequence test; // A sequence that we’ll perform tests on
    char choice;   // A command character entered by the user

    cout << "I have initialized an empty sequence of real numbers." << endl;

    do
    {
        print_menu( );
        choice = toupper(get_user_command( ));
        switch (choice)
        {
            case '!': test.start( );
                      break;
            case '+': test.advance( );
                      break;
            case '?': if (test.is_item( ))
                          cout << "There is an item." << endl;
                      else 
                          cout << "There is no current item." << endl;
                      break;
            case 'C': if (test.is_item( ))
                           cout << "Current item is: " << test.current( ) << endl;
                      else
                          cout << "There is no current item." << endl;
                      break;
            case 'P': show_sequence(test);
                      break;
            case 'S': cout << "Size is " << test.size( ) << '.' << endl;
                      break;
            case 'I': test.insert(get_number( ));
                      break;
            case 'A': test.attach(get_number( ));
                      break;
            case 'R': test.remove_current( );
                      cout << "The current item has been removed." << endl;
                      break;     
            case 'Q': cout << "Ridicule is the best test of truth." << endl;
                      break;
            default:  cout << choice << " is invalid." << endl;
        }
    }
    while ((choice != 'Q'));

    return EXIT_SUCCESS;
}

void print_menu( )
// Library facilities used: iostream.h
{
    cout << endl; // Print blank line before the menu
    cout << "The following choices are available: " << endl;
    cout << " !   Activate the start( ) function" << endl;
    cout << " +   Activate the advance( ) function" << endl;
    cout << " ?   Print the result from the is_item( ) function" << endl;
    cout << " C   Print the result from the current( ) function" << endl;
    cout << " P   Print a copy of the entire sequence" << endl;
    cout << " S   Print the result from the size( ) function" << endl;
    cout << " I   Insert a new number with the insert(...) function" << endl;
    cout << " A   Attach a new number with the attach(...) function" << endl;
    cout << " R   Activate the remove_current( ) function" << endl;
    cout << " Q   Quit this test program" << endl;
}

char get_user_command( )
// Library facilities used: iostream
{
    char command;

    cout << "Enter choice: ";
    cin >> command; // Input of characters skips blanks and newline character

    return command;
}

void show_sequence(sequence display)
// Library facilities used: iostream
{
    for (display.start( ); display.is_item( ); display.advance( ))
        cout << display.current( ) << endl;
}

double get_number( )
// Library facilities used: iostream
{
    double result;

    cout << "Please enter a real number for the sequence: ";
    cin  >> result;
    cout << result << " has been read." << endl;
    return result;
}

when i click the option P in the debuger to print the whole sequence out it never works right and often spits out garbage and when i click c in the debugger menu after insirting or attaching 2 numbers it doesnt seem to work right either. i analized my algorithms and i dont understand why they arent working right..

Answer 1

Summary:

You are creating an instance of the class sequence using the default constructor which doesn't allocate the array you store the numbers in, this will cause incorrect behaviour when calling any of the functions from the menu causes because they depend on the array to be initialized correctly. What you need to do is to create the test instance using another constructor, namely the one taking an size argument.

Original text

From looking the "test debugger file" above I notice that you call the default constructor for the class sequence:

sequence test; // A sequence that we’ll perform tests on

Looking at the implementation, I can't find that have implemented it. I think that the constructor:

sequence(size_type entry=CAPACITY )

is what you need to call in order to "new" the underlying array data and set the indexes correctly at startup. The current code will for example upon calling show_sequence(test) read data from uninitialized random memory.