Changing an array class to hold a dynamic array - c++

Question

everything i have read says this should be easy and that you just add these three lines
typedef double* DoublePtr;
DoublePtr p;
p = new double [10]
but where do i add this code? Everything i have tried just breaks my program what am I missing? I tried a set function to set the value of max size but it didn't work either
does anyone know how to do this?
#include<iostream>
using namespace std;
const int MAX_SIZE = 50;
class ListDynamic
{
public:
ListDynamic();
bool full();
int getSize();
void addValue(double value);
double getValue(int index);
double getLast();
void deleteLast();
friend ostream& operator <<(ostream& out, const ListDynamic& thisList);
private:
double listValues[MAX_SIZE];
int size;
};
int main()
{
double value;
ListDynamic l;
cout << "size of List " << l.getSize() << endl;
cout << "New size of List " << l.getSize() << endl;
cout << "First Value: " << l.getValue(0) << endl;
cout << "Last Value: " << l.getLast() << endl;
cout << "deleting last value from list" << endl;
l.deleteLast();
cout << "new list size " << l.getSize() << endl;
cout << "the list now contains: " << endl << l << endl;
system("pause");
return 0;
}
ListDynamic::ListDynamic()
{
size = 0;
}
bool ListDynamic::full()
{
return (size == MAX_SIZE);
}
int ListDynamic::getSize()
{
return size;
}
void ListDynamic::addValue(double value)
{
if (size < MAX_SIZE)
{
listValues[size] = value;
size++;
}
else
cout << "\n\n*** Error in ListDynamic Class: Attempting to add value past max limit.";
}
double ListDynamic::getValue(int index)
{
if (index < size)
return listValues[index];
else
cout << "\n\n*** Error in ListDynamic Class: Attempting to retrieve value past current size.";
}
double ListDynamic::getLast()
{
if (size > 0)
return getValue(size - 1);
else
cout << "\n\n*** Error in ListDynamic Class: Call to getLast in Empty List.";
}
void ListDynamic::deleteLast()
{
if (size > 0)
size--;
else
cout << "\n\n*** Error in ListDynamic Class: Call to deleteLast in Empty List.";
}
ostream& operator <<(ostream& out, const ListDynamic& thisList)
{
for (int i = 0; i < thisList.size; i++)
out << thisList.listValues[i] << endl;
return out;
}

Answer 1

You need to change listValues to a double*
double* listValues;
And when you add a value greater than the size, you'll need to reallocate the array your array and copy the elements of the former array to the new one. For example:
void ListDynamic::addValue(double value)
{
if (full())
{
double* temp = new double[size];
std::copy(listValues, listValues + size, temp);
delete[] listValues;
listValues = new double[size + 1];
std::copy(temp, temp + size, listValues);
listValues[size] = value;
delete[] temp;
} else
{
listValues[size++] = value;
}
}