Making an array class so they act like vectors - c++

Question

I have to make a class that will make arrays act like vectors. When I try and pass the class into the method into my main I get an error telling me that "[" and "]" are incorrect operators. I was wondering if I'm just completely doing this wrong or if it's just a simple mistake. Help is greatly appreciated. Here is my header file:
#ifndef PROGRAM5HEADER_H
#ifndef PROGRAM5HEADER_H
#define PROGRAM5HEADER_H
#include <string>
using namespace std;
class FloatArray
{
int *rep;
int _size;
public:
FloatArray(int sz=100):_size(sz)
{
rep=new int[sz];
}
~FloatArray()
{
delete [] rep;
}
int size() const
{
return _size;
}
FloatArray(const FloatArray& x)
{
copy(x);
}
void copy(const FloatArray& x)
{
_size == x.size();
rep=new int[_size];
for(int k=0;k<_size;k++)
rep[k]=x.rep[k];
}
};
#endif
and here is my main program
#include <iostream>
#include <string>
#include <cstdlib>
#include "program5header.h"
#include <cmath>
using namespace std;
int meanstd(FloatArray x, int& std)
{
int sx=0,sx2=0,mean;
for(int i=0;i<x.size();i++)
{
sx+=x[i];
sx2+=x[i]*x[i];
}
mean=sx/x.size();
std=sqrt(sx2/x.size()-mean*mean);
return mean;
}
int main()
{ int f;
cout<<"How big of an array would you like: "<<endl;
cin>>f;
FloatArray x(f);
}

Answer 1

There are a lot of issues with a lot of your implementation, I'd suggest doing some research on the subject. I'll touch on a few.
Firstly, you should make your FloatArray a templated class and allow for different types other than just int.
When you initialize a FloatArray x and then try to access it's underlying array through "[]" you are actually invoking the following:
x.operator[](...)
You haven't defined the '[]' operator on your FloatArray class so you are getting an error.
You need something similar to this:
int FloatArray.operator[](int index) {
assert(index < _size);
return _rep[index]
}
Your copy isn't doing what you want, it's not copying the size over to "this". It should look something similar to this:
void copy(const FloatArray& x)
{
_size = x._size;
rep=new int[_size];
for(int k=0;k<_size;k++)
rep[k]=x.rep[k];
}
However I would suggest not having a copy method and instead implement everything in your copy constructor.