Am I doing something wrong here (references in C++)?

Question

I've been playing around with references (I'm still having issues in this regard).

1- I would like to know if this is an acceptable code:

int & foo(int &y)
{
    return y;  // is this wrong?
}

int main()
{
    int x = 0;    
    cout << foo(x) << endl;

    foo(x) = 9;   // is this wrong?
    cout << x << endl;

    return 0;
}

2- Also this is from an exam sample:

Week & Week::highestSalesWeek(Week aYear[52])
{
  Week max = aYear[0];
  for(int i = 1; i < 52; i++)
  {
    if (aYear[i].getSales() > max.getSales())
      max = aYear[i];
  }
  return max;
}

It asks about the mistake in this code, also how to fix it.

My guess is that it return a local reference. The fix is:

Week & max = aYear[0];

Is this correct/enough?

Answer 1

The first one is correct.

For the second one, there are infinite number of solutions :), but this would be mine:

Week Week::highestSalesWeek(Week aYear[52]) // return a copy of the week
{ 
  Week max = aYear[0]; 
  for(int i = 1; i < 52; i++) 
  { 
    if (aYear[i].getSales() > max.getSales()) max = aYear[i]; 
  } 
  return max; 
} 

If max is a reference, you would modify the first element of aYear everytime you do:

max = aYear[i]

Also, you could use a pointer to return a reference to the week:

Week & Week::highestSalesWeek(Week aYear[52])
{ 
  Week* max = &aYear[0]; 
  for(int i = 1; i < 52; i++) 
  { 
    if (aYear[i].getSales() > max->getSales()) max = &aYear[i]; 
  } 
  return *max; 
}