I was given a header file and the main files i have to create the implementation file for the header file

I am issues trying to find out where I went wrong in my for loops. Can you point me in the right direction

The header file

// FILE: sequence1.h
// CLASS PROVIDED: sequence (part of the namespace main_savitch_3)
// There is no implementation file provided for this class since it is
// an exercise from Section 3.2 of "Data Structures and Other Objects Using C++"
//
// TYPEDEFS and MEMBER CONSTANTS for the sequence class:
//   typedef ____ value_type
//     sequence::value_type is the data type of the items in the sequence. It
//     may be any of the C++ built-in types (int, char, etc.), or a class with a
//     default constructor, an assignment operator, and a copy constructor.
//
//   typedef ____ size_type
//     sequence::size_type is the data type of any variable that keeps track of
//     how many items are in a sequence.
//
//   static const size_type CAPACITY = _____
//     sequence::CAPACITY is the maximum number of items that a sequence can hold.
//
// CONSTRUCTOR for the sequence class:
//   sequence( )
//     Postcondition: The sequence has been initialized as an empty sequence.
//
// MODIFICATION MEMBER FUNCTIONS for the sequence class:
//   void start( )
//     Postcondition: The first item on the sequence becomes the current item
//     (but if the sequence is empty, then there is no current item).
//
//   void advance( )
//     Precondition: is_item returns true.
//     Postcondition: If the current item was already the last item in the
//     sequence, then there is no longer any current item. Otherwise, the new
//     current item is the item immediately after the original current item.
//
//   void insert(const value_type& entry)
//     Precondition: size( ) < CAPACITY.
//     Postcondition: A new copy of entry has been inserted in the sequence
//     before the current item. If there was no current item, then the new entry 
//     has been inserted at the front of the sequence. In either case, the newly
//     inserted item is now the current item of the sequence.
//
//   void attach(const value_type& entry)
//     Precondition: size( ) < CAPACITY.
//     Postcondition: A new copy of entry has been inserted in the sequence after
//     the current item. If there was no current item, then the new entry has 
//     been attached to the end of the sequence. In either case, the newly
//     inserted item is now the current item of the sequence.
//
//   void remove_current( )
//     Precondition: is_item returns true.
//     Postcondition: The current item has been removed from the sequence, and the
//     item after this (if there is one) is now the new current item.
//
// CONSTANT MEMBER FUNCTIONS for the sequence class:
//   size_type size( ) const
//     Postcondition: The return value is the number of items in the sequence.
//
//   bool is_item( ) const
//     Postcondition: A true return value indicates that there is a valid
//     "current" item that may be retrieved by activating the current
//     member function (listed below). A false return value indicates that
//     there is no valid current item.
//
//   value_type current( ) const
//     Precondition: is_item( ) returns true.
//     Postcondition: The item returned is the current item in the sequence.
//
// VALUE SEMANTICS for the sequence class:
//    Assignments and the copy constructor may be used with sequence objects.

#ifndef MAIN_SAVITCH_SEQUENCE_H
#define MAIN_SAVITCH_SEQUENCE_H
#include <cstdlib>  // Provides size_t

namespace main_savitch_3
{
    class sequence
    {
    public:
        // TYPEDEFS and MEMBER CONSTANTS
        typedef double value_type;
        typedef std::size_t size_type;
        static const size_type CAPACITY = 30;
        // CONSTRUCTOR
        sequence( );
        // MODIFICATION MEMBER FUNCTIONS
        void start( );
        void advance( );
        void insert(const value_type& entry);
        void attach(const value_type& entry);
        void remove_current( );
        // CONSTANT MEMBER FUNCTIONS
        size_type size( ) const;
        bool is_item( ) const;
        value_type current( ) const;
    private:
        value_type data[CAPACITY];
        size_type used;
        size_type current_index;
    };
}

#endif

My Implementation File

#include <iostream>
#include <cassert> // Provides assert function
#include "sequence1.h" // With value_type defined as double
using namespace std;
 
namespace main_savitch_3
{
  
// MODIFICATION MEMBER FUNCTIONS
  sequence::sequence ()
  {
    current_index = 0;
    used = 0; 
  }
 
  void sequence::start( )
  {
    current_index = 0;
  }
 
  void sequence::advance( )
  {
    current_index++;
  }
 
  void sequence::insert(const value_type& entry)
  {
    int i;
    
   for (i = used; i < current_index; i--)
    {
      data[i]= data[i-1];
      data[current_index] = entry;
      used++;
    }


  }
 
  void sequence::attach(const value_type& entry)
  {
    int i;
    
    for (i = used; i < current_index; i--)
    {
      data[i] = data[i+1];
      data[current_index] = entry;
      used++;
    }


  }
 
  void sequence::remove_current( )
  {
    int i;
    
   
    for (i= current_index +1; i < used -1; i++)
    {
      data[i] = data[i+1];
      used--;
    }

  }
 
 
// CONSTANT MEMBER FUNCTIONS
  sequence::size_type sequence::size( ) const
  {
    return used; 
  }
 
  bool sequence::is_item( ) const
  {    
    return current_index < used;
  }
 
  sequence::value_type sequence::current( ) const
  {    
    return data[current_index];
  }
}

The Main file

// FILE: sequence_exam.cxx
// Written by: Michael Main (main@colorado.edu) - Oct 22, 1997
// Non-interactive test program for the sequence class from Section 3.2 of
// "Data Structures and Other Objects".
//
// Each function of this program tests part of the sequence class, returning
// some number of points to indicate how much of the test was passed.
// A description and result of each test is printed to cout.
//
// Maximum number of points awarded by this program is determined by the
// constants POINTS[1], POINTS[2]...


#include <iostream>   // Provides cout.
#include <cstdlib>    // Provides size_t.
#include "sequence1.h"    // Provides the sequence class with double items.
using namespace std;
using namespace main_savitch_3;

// Descriptions and points for each of the tests:
const size_t MANY_TESTS = 3;
const int POINTS[MANY_TESTS+1] = {
    100, // Total points for all tests.
    50,  // Test 1 points
    25,  // Test 2 points
    25   // Test 3 points
};
const char DESCRIPTION[MANY_TESTS+1][256] = {
    "tests for Chapter 3 sequence Class",
    "Testing insert, attach, and the constant member functions",
    "Testing situations where the cursor goes off the sequence",
    "Testing remove_current"
};


// **************************************************************************
// bool test_basic(const sequence& test, size_t s, bool has_cursor)
//   Postcondition: A return value of true indicates:
//     a. test.size() is s, and
//     b. test.is_item() is has_cursor.
//   Otherwise the return value is false.
//   In either case, a description of the test result is printed to cout.
// **************************************************************************
bool test_basic(const sequence& test, size_t s, bool has_cursor)
{
    bool answer;

    cout << "Testing that size() returns " << s << " ... ";
    cout.flush( );
    answer = (test.size( ) == s);
    cout << (answer ? "Passed." : "Failed.") << endl;

    if (answer)
    {
        cout << "Testing that is_item() returns ";
        cout << (has_cursor ? "true" : "false") << " ... ";
        cout.flush( );
        answer = (test.is_item( ) == has_cursor);
        cout << (answer ? "Passed." : "Failed.") << endl;
    }

    return answer;
}


// **************************************************************************
// bool test_items(sequence& test, size_t s, size_t i, double items[])
//   The function determines if the test sequence has the correct items
//   Precondition: The size of the items array is at least s.
//   Postcondition: A return value of true indicates that test.current()
//   is equal to items[i], and after test.advance() the result of
//   test.current() is items[i+1], and so on through items[s-1].
//   At this point, one more advance takes the cursor off the sequence.
//   If any of this fails, the return value is false.
//   NOTE: The test sequence has been changed by advancing its cursor.
// **************************************************************************
bool test_items(sequence& test, size_t s, size_t i, double items[])
{
    bool answer = true;

    cout << "The cursor should be at item [" << i << "]" << " of the sequence\n";
    cout << "(counting the first item as [0]). I will advance the cursor\n";
    cout << "to the end of the sequence, checking that each item is correct...";
    cout.flush( );
    while ((i < s) && test.is_item( ) && (test.current( ) == items[i]))
    {
        i++;
        test.advance( );
    }

    if ((i != s) && !test.is_item( ))
    {   // The test.is_item( ) function returns false too soon.
        cout << "\n    Cursor fell off the sequence too soon." << endl;
        answer = false;
    }
    else if (i != s)
    {   // The test.current( ) function returned a wrong value.
        cout << "\n    The item [" << i << "] should be " << items[i] << ",\n";
        cout << "    but it was " << test.current( ) << " instead.\n";
        answer = false;
    }
    else if (test.is_item( ))
    {   // The test.is_item( ) function returns true after moving off the sequence.
        cout << "\n    The cursor was moved off the sequence,";
        cout << " but is_item still returns true." << endl;
        answer = false;
    }

    cout << (answer ? "Passed." : "Failed.") << endl;
    return answer;
}


// **************************************************************************
// bool correct(sequence test, size_t s, size_t cursor_spot, double items[])
//   This function determines if the sequence (test) is "correct" according to
//   these requirements:
//   a. it has exactly s items.
//   b. the items (starting at the front) are equal to
//      double[0] ... double[size-1]
//   c. if cursor_spot < size, then test's cursor must be at
//      the location given by cursor_spot.
//   d. if cursor_spot >= size, then test must not have a cursor.
// NOTE: The function also moves the cursor off the sequence.
// **************************************************************************
bool correct(sequence& test, size_t size, size_t cursor_spot, double items[])
{
    bool has_cursor = (cursor_spot < size);

    // Check the sequence's size and whether it has a cursor.
    if (!test_basic(test, size, has_cursor))
    {
        cout << "Basic test of size() or is_item() failed." << endl << endl;
        return false;
    }

    // If there is a cursor, check the items from cursor to end of the sequence.
    if (has_cursor && !test_items(test, size, cursor_spot, items))
    {
        cout << "Test of the sequence's items failed." << endl << endl;
        return false;
    }

    // Restart the cursor at the front of the sequence and test items again.
    cout << "I'll call start() and look at the items one more time..." << endl;
    test.start( );
    if (has_cursor && !test_items(test, size, 0, items))
    {
        cout << "Test of the sequence's items failed." << endl << endl;
        return false;
    }

    // If the code reaches here, then all tests have been passed.
    cout << "All tests passed for this sequence." << endl << endl;
    return true;
}


// **************************************************************************
// int test1( )
//   Performs some basic tests of insert, attach, and the constant member
//   functions. Returns POINTS[1] if the tests are passed. Otherwise returns 0.
// **************************************************************************
int test1( )
{
    sequence empty;                            // An empty sequence
    sequence test;                             // A sequence to add items to
    double items1[4] = { 5, 10, 20, 30 };  // These 4 items are put in a sequence
    double items2[4] = { 10, 15, 20, 30 }; // These are put in another sequence

    // Test that the empty sequence is really empty
    cout << "Starting with an empty sequence." << endl;
    if (!correct(empty, 0, 0, items1)) return 0;

    // Test the attach function to add something to an empty sequence
    cout << "I am now using attach to put 10 into an empty sequence." << endl;
    test.attach(10);
    if (!correct(test, 1, 0, items2)) return 0;

    // Test the insert function to add something to an empty sequence
    cout << "I am now using insert to put 10 into an empty sequence." << endl;
    test = empty;
    test.insert(10);
    if (!correct(test, 1, 0, items2)) return 0;

    // Test the insert function to add an item at the front of a sequence
    cout << "I am now using attach to put 10,20,30 in an empty sequence.\n";
    cout << "Then I move the cursor to the start and insert 5." << endl;
    test = empty;
    test.attach(10);
    test.attach(20);
    test.attach(30);
    test.start( );
    test.insert(5);
    if (!correct(test, 4, 0, items1)) return 0;

    // Test the insert function to add an item in the middle of a sequence
    cout << "I am now using attach to put 10,20,30 in an empty sequence.\n";
    cout << "Then I move the cursor to the start, advance once, ";
    cout << "and insert 15." << endl;
    test = empty;
    test.attach(10);
    test.attach(20);
    test.attach(30);
    test.start( );
    test.advance( );
    test.insert(15);
    if (!correct(test, 4, 1, items2)) return 0;

    // Test the attach function to add an item in the middle of a sequence
    cout << "I am now using attach to put 10,20,30 in an empty sequence.\n";
    cout << "Then I move the cursor to the start and attach 15 ";
    cout << "after the 10." << endl;
    test = empty;
    test.attach(10);
    test.attach(20);
    test.attach(30);
    test.start( );
    test.attach(15);
    if (!correct(test, 4, 1, items2)) return 0;

    // All tests have been passed
    cout << "All tests of this first function have been passed." << endl;
    return POINTS[1];
}


// **************************************************************************
// int test2( )
//   Performs a test to ensure that the cursor can correctly be run off the end
//   of the sequence. Also tests that attach/insert work correctly when there is
//   no cursor. Returns POINTS[2] if the tests are passed. Otherwise returns 0.
// **************************************************************************
int test2( )
{
    sequence test;
    size_t i;

    // Put three items in the sequence
    cout << "Using attach to put 20 and 30 in the sequence, and then calling\n";
    cout << "advance, so that is_item should return false ... ";
    cout.flush( );
    test.attach(20);
    test.attach(30);
    test.advance( );
    if (test.is_item( ))
    {
        cout << "failed." << endl;
        return 0;
    }
    cout << "passed." << endl;

    // Insert 10 at the front and run the cursor off the end again
    cout << "Inserting 10, which should go at the sequence's front." << endl;
    cout << "Then calling advance three times to run cursor off the sequence ...";
    cout.flush( );
    test.insert(10);
    test.advance( ); // advance to the 20
    test.advance( ); // advance to the 30
    test.advance( ); // advance right off the sequence
    if (test.is_item( ))
    {
        cout << " failed." << endl;
        return false;
    }
    cout << " passed." << endl;

    // Attach more items until the sequence becomes full.
    // Note that the first attach should attach to the end of the sequence.
    cout << "Calling attach to put the numbers 40, 50, 60 ...";
    cout << test.CAPACITY*10 << " at the sequence's end." << endl;
    for (i = 4; i <= test.CAPACITY; i++)
        test.attach(i*10);

    // Test that the sequence is correctly filled.
    cout << "Now I will test that the sequence has 10, 20, 30, ...";
    cout << test.CAPACITY*10 << "." << endl;
    test.start( );
    for (i = 1; i <= test.CAPACITY; i++)
    {
        if ((!test.is_item( )) || test.current( ) != i*10)
        {
            cout << "    Test failed to find " << i*10 << endl;
            return 0;
        }
        test.advance( );
    }
    if (test.is_item( ))
    {
        cout << "    There are too many items on the sequence." << endl;
        return false;
    }

    // All tests passed
    cout << "All tests of this second function have been passed." << endl;
    return POINTS[2];
}


// **************************************************************************
// int test3( )
//   Performs basic tests for the remove_current function.
//   Returns POINTS[3] if the tests are passed. Returns POINTS[3] / 4 if almost
//   all the tests are passed. Otherwise returns 0.
// **************************************************************************
int test3( )
{
    // In the next declarations, I am declaring a sequence called test.
    // Both before and after the sequence, I declare a small array of characters,
    // and I put the character 'x' into each spot of these arrays.
    // Later, if I notice that one of the x's has been changed, or if
    // I notice an 'x' inside of the sequence, then the most
    // likely reason was that one of the sequence's member functions accessed
    // the sequence's array outside of its legal indexes.
    char prefix[4] = {'x', 'x', 'x', 'x'};
    sequence test;
    char suffix[4] = {'x', 'x', 'x', 'x'};

    // Within this function, I create several different sequences using the
    // items in these arrays:
    double items1[1] = { 30 };
    double items2[2] = { 10, 30 };
    double items3[3] = { 10, 20, 30 };

    size_t i;       // for-loop control variable
    char *char_ptr; // Variable to loop at each character in a sequence's memory

    // Build a sequence with three items 10, 20, 30, and remove the middle,
    // and last and then first.
    cout << "Using attach to build a sequence with 10,30." << endl;
    test.attach(10);
    test.attach(30);
    cout << "Insert a 20 before the 30, so entire sequence is 10,20,30." << endl;
    test.insert(20);
    if (!correct(test, 3, 1, items3)) return 0;
    cout << "Remove the 20, so entire sequence is now 10,30." << endl;
    test.start( );
    test.advance( );
    test.remove_current( );
    if (!correct(test, 2, 1, items2)) return 0;
    cout << "Remove the 30, so entire sequence is now just 10 with no cursor.";
    cout << endl;
    test.start( );
    test.advance( );
    test.remove_current( );
    if (!correct(test, 1, 1, items2)) return 0;
    cout << "Set the cursor to the start and remove the 10." << endl;
    test.start( );
    test.remove_current( );
    if (!correct(test, 0, 0, items2)) return 0;

    // Build a sequence with three items 10, 20, 30, and remove the middle,
    // and then first and then last.
    cout << "Using attach to build another sequence with 10,30." << endl;
    test.attach(10);
    test.attach(30);
    cout << "Insert a 20 before the 30, so entire sequence is 10,20,30." << endl;
    test.insert(20);
    if (!correct(test, 3, 1, items3)) return 0;
    cout << "Remove the 20, so entire sequence is now 10,30." << endl;
    test.start( );
    test.advance( );
    test.remove_current( );
    if (!correct(test, 2, 1, items2)) return 0;
    cout << "Set the cursor to the start and remove the 10," << endl;
    cout << "so the sequence should now contain just 30." << endl;
    test.start( );
    test.remove_current( );
    if (!correct(test, 1, 0, items1)) return 0;
    cout << "Remove the 30 from the sequence, resulting in an empty sequence." << endl;
    test.start( );
    test.remove_current( );
    if (!correct(test, 0, 0, items1)) return 0;

    // Build a sequence with three items 10, 20, 30, and remove the first.
    cout << "Build a new sequence by inserting 30, 10, 20 (so the sequence\n";
    cout << "is 20, then 10, then 30). Then remove the 20." << endl;
    test.insert(30);
    test.insert(10);
    test.insert(20);
    test.remove_current( );
    if (!correct(test, 2, 0, items2)) return 0;
    test.start( );
    test.remove_current( );
    test.remove_current( );

    // Just for fun, fill up the sequence, and empty it!
    cout << "Just for fun, I'll empty the sequence then fill it up, then\n";
    cout << "empty it again. During this process, I'll try to determine\n";
    cout << "whether any of the sequence's member functions access the\n";
    cout << "array outside of its legal indexes." << endl;
    for (i = 0; i < test.CAPACITY; i++)
        test.insert(0);
    for (i = 0; i < test.CAPACITY; i++)
        test.remove_current( );

    // Make sure that the character 'x' didn't somehow get into the sequence,
    // as that would indicate that the sequence member functions are
    // copying data from before or after the sequence into the sequence.
    char_ptr = (char *) &test;
    for (i = 0; i < sizeof(sequence); i++)
        if (char_ptr[i] == 'x')
        {
            cout << "Illegal array access detected." << endl;
            return POINTS[3] / 4;
        }

    // Make sure that the prefix and suffix arrays still have four
    // x's each. Otherwise one of the sequence operations wrote outside of
    // the legal boundaries of its array.
    for (i = 0; i < 4; i++)
        if ((suffix[i] != 'x') || (prefix[i] != 'x'))
        {
            cout << "Illegal array access detected." << endl;
            return POINTS[3] / 4;
        }

    // All tests passed
    cout << "All tests of this third function have been passed." << endl;
    return POINTS[3];
}


int run_a_test(int number, const char message[], int test_function( ), int max)
{
    int result;

    cout << endl << "START OF TEST " << number << ":" << endl;
    cout << message << " (" << max << " points)." << endl;
    result = test_function( );
    if (result > 0)
    {
        cout << "Test " << number << " got " << result << " points";
        cout << " out of a possible " << max << "." << endl;
    }
    else
        cout << "Test " << number << " failed." << endl;
    cout << "END OF TEST " << number << "." << endl << endl;

    return result;
}


// **************************************************************************
// int main( )
//   The main program calls all tests and prints the sum of all points
//   earned from the tests.
// **************************************************************************
int main( )
{
    int sum = 0;


    cout << "Running " << DESCRIPTION[0] << endl;

    sum += run_a_test(1, DESCRIPTION[1], test1, POINTS[1]);
    sum += run_a_test(2, DESCRIPTION[2], test2, POINTS[2]);
    sum += run_a_test(3, DESCRIPTION[3], test3, POINTS[3]);

    cout << "If you submit the Chapter 3 sequence now, you will have\n";
    cout << sum << " points out of the " << POINTS[0];
    cout << " points from this test program.\n";

    return EXIT_SUCCESS;

}

just a suggestion to get you going...
on your attach and insert, try making i > current_index. Your working the other side of the for loop.
And take the data[current_index] and used++ parts out of the for loop and put it after.
Take it from there and you still need a little more work, but that should help. I'm not going to give you all the answers so you can still work on it.

Thank you I also realized that when I went through the code i realized that --i and i-- are two different things once you told me where to look at

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