I am getting a error [ error: expected unqualified-id before ‘&’ token ] in a c++ program

I am getting a unusual error:

error: expected unqualified-id before ‘&’ token

Source code:

// Overloading the c++ array subscript operator [ ]

#include<iostream>
using namespace std;

const int size=10;

class myArray
{
      int a[size];
    public:
      myArray()
      {}
      int & operator [](int);
      void print_array();   
};

int myArray & operator [](int x) // This is the line where error is as by compiler
{
          return a[x];
}

void myArray::print_array()
{
    for (int j=0; j < 10; j++)
        cout<<"array["<<j<<"] = "<<a[j]<<"\n";
}

int main()
{
    myArray instance;
    for (int i=0; i < size; i++)
     {
       instance[i] = i;
     }  
    instance.print_array();

开发者_JS百科    cout<<"\n\n";
    return 0;
}

You need to tell the compiler that your operator [] function is a member of myArray:

int & myArray::operator [](const int x) 
{
          return a[x];
}

For more info, this page has decent examples.

The problem is with your definition of the operator []

int myArray & operator [](int x) // This is the line where error is as by compiler
{
          return a[x];
}

Should be:

int & myArray::operator [](const int x) 
{
          return a[x];
}

Also, as an suggestion [] is usually overloaded so as to avoid crossing the array bounds. So your [] overloading should ideally check x against size before dereferencing the array at that index. Without such an checking the whole purpose of overloading the [] is defeated.