Homework task: Checking the equality of two arrays - c++

Question

I am stuck on a homework question which requires me to create/modify a function which will set two arrays equal to each other. The question asks:
"Use the copy assignment (=) operator to set the two arrays equal to each other, this can be checked with the following:
y = x;
cout << "x equals y? " << (x == y) << endl; //Should return "True"
And is set within the following rules:
"Note that two Array objects should be considered equal only if they have the same length and the same element values."
This is the code I have, I have implemented two debugging sections which shows that they are indeed equal both in the assignment function and the main function, so my best guess is that the lengths don't match up. I am not allowed to modify any of the code which was provided (All the class and function stuff, or anything above the debugger in main), so I'm not sure how to set the lengths equal to each other in order to satisfy the condition (x==y)
#include <iostream>
using namespace std;
// definition
#define MAX_LENGTH 100
#define INIT_VALUE 0
class Array {
public:
Array(int length);
Array& operator=(const Array& other);
int length() const;
int& operator[](int index);
bool operator==(const Array& other) const;
bool operator!=(const Array& other) const;
private:
int length_;
int elements_[MAX_LENGTH];
};
// implementation
Array::Array(int length) {
length_ = length;
if (length_ > MAX_LENGTH) length_ = MAX_LENGTH;
for (int i = 0; i < length_; ++i) {
elements_[i] = INIT_VALUE;
}
}
Array& Array::operator=(const Array& other)
{
/*DEBUG*/cout << endl << endl << "<<NOW IN ASSIGNMENT FUNCTION>>" << endl << endl;
for (int i = 0; i < other.length_; ++i)
{
elements_[i] = other.elements_[i];
/*DEBUG*/cout << endl << "Elements: " << elements_[i] << " | Other Elements: " << other.elements_[i] << endl;
}
return *this;
}
int Array::length() const {
return length_;
}
int& Array::operator[](int index) {
// Q3 code goes here
return elements_[index];
}
bool Array::operator==(const Array& other) const
{
if (length_ != other.length_) return false;
for (int i = 0; i < other.length_; ++i) {
if (elements_[i] != other.elements_[i]) return false;
}
return true;
}
bool Array::operator!=(const Array& other) const
{
if (length_ != other.length_)
{
return true;
}
for (int j = 0; j < other.length_; ++j)
{
if (elements_[j] != other.elements_[j]) return true;
}
return false;
}
// testing
int main()
{
Array x(10);
x[3] = 42;
cout << "x contains ";
for (int i = 0; i < x.length(); ++i) {
cout << x[i] << " ";
}
cout << endl;
Array y(5);
cout << boolalpha;
cout << "x equals y? " << (x == y) << endl;
cout << "x notequals y? " << (x != y) << endl;
y = x;
//DEBUG SECTION
cout << endl << endl << "<<NOW IN MAIN>>" << endl << endl;
for (int i = 0; i < x.length(); ++i)
{
cout << endl << "Elements: " << x[i] << " | Other Elements: " << y[i] << endl;
}
//END OF DEBUG SECTION
cout << "x equals y? " << (x == y) << endl;
}
So the question is, how can I get these arrays to have the same length without modifying them in 'main'? Can I do this through the assignment function?

Answer 1

You just forgot to assign the same length in the the Array::operator=.
This can be done by writing this->length_ = other.length_; in the
Array& Array::operator=(const Array& other) before overwriting the array.

Answer 2

As mentioned before, you did not asign the length correctly in the = operator.
Fix like this:
Array& Array::operator=(const Array& other)
{
length_ = other.length_;
for (int i = 0; i < length_; ++i)
{
elements_[i] = other.elements_[i];
}
return *this;
}
Also you can simplify your != operator drastically
bool Array::operator!=(const Array& other) const
{
return !(*this == other);
}
However, in my opinon even more important, you should also make use of the std-containers which allow dynamic sizes such as std::vector. This also would have avoided your bug.
In my opinion you should use these std-containers as soon as possible and get used to them. They are almost always the right choice when in doubt.
With std::vector your program could look like this:
#include <iostream>
#include <vector>
using namespace std;
// definition
#define INIT_VALUE 0
class Array {
public:
Array(int length);
Array& operator=(const Array& other);
int length() const;
int& operator[](int index);
bool operator==(const Array& other) const;
bool operator!=(const Array& other) const;
private:
std::vector<int> elements_;
};
// implementation
Array::Array(int length)
:
elements_(length, INIT_VALUE)
{
}
Array& Array::operator=(const Array& other)
{
/*DEBUG*/cout << endl << endl << "<<NOW IN ASSIGNMENT FUNCTION>>" << endl << endl;
elements_ = other.elements_;
return *this;
}
int Array::length() const {
return static_cast<int>(elements_.size());
}
int& Array::operator[](int index) {
// Q3 code goes here
return elements_[index];
}
bool Array::operator==(const Array& other) const
{
return elements_ == other.elements_;
}
bool Array::operator!=(const Array& other) const
{
return !(*this == other);
}
// testing
int main()
{
Array x(10);
x[3] = 42;
cout << "x contains ";
for (int i = 0; i < x.length(); ++i) {
cout << x[i] << " ";
}
cout << endl;
Array y(5);
cout << boolalpha;
cout << "x equals y? " << (x == y) << endl;
cout << "x notequals y? " << (x != y) << endl;
y = x;
//DEBUG SECTION
cout << endl << endl << "<<NOW IN MAIN>>" << endl << endl;
for (int i = 0; i < x.length(); ++i)
{
cout << endl << "Elements: " << x[i] << " | Other Elements: " << y[i] << endl;
}
//END OF DEBUG SECTION
cout << "x equals y? " << (x == y) << endl;
}