Re: Overloading << operator

From:
Norbert Unterberg <nunterberg@newsgroups.nospam>
Newsgroups:
microsoft.public.vc.language
Date:
Sun, 17 Feb 2008 12:28:15 +0100
Message-ID:
<ORgIzgVcIHA.5900@TK2MSFTNGP02.phx.gbl>
Christian schrieb:

Hi I have this code:

[CODE]
template <class T>
ostream& operator<< (ostream& output, Array<T>& theArray)
{
    for (int i = 0; i<theArray.GetSize(); i++)
        output << "[" << i << "] " << theArray[i] << endl;
}
[/CODE]

which is defined as:

[CODE]
template <class T> friend ostream& operator<< (ostream&, Array<T>&);
[/CODE]

By compiling the source code VS2005 tells me:

 error C4716: 'operator<<<int>' : must return a value.


Sure. You created a function that returns an ostream&, but your function does
not contain a return statement.

Add
    return output;
to the end of your function.

Norbert

It seems as it can't recognize ostream& as a returned value. By
reading this article [1] it seems that there's nothing wrong in my
code,so what's the problem? Thanks.

FULL CODE:

#include "stdafx.h"
#include <iostream>

using namespace std;

const int DefaultSize = 10;

template <class T> // declare the template and the parameter
class Array // the class being parameterized
{
public:
    // constructors
    Array(int itsSize = DefaultSize);
    Array(const Array &rhs);
    ~Array() { delete [] pType; }

    // operators
    Array& operator=(const Array&);
    T& operator[](int offSet) { return pType[offSet]; }
    const T& operator[](int offSet) const { return pType[offSet]; }

    // accessors
    int GetSize() const { return itsSize; }

    template <class T> friend ostream& operator<< (ostream&, Array<T>&);

private:
    T *pType;
    int itsSize;
};

template <class T>
ostream& operator<< (ostream& output, Array<T>& theArray)
{
    for (int i = 0; i<theArray.GetSize(); i++)
        output << "[" << i << "] " << theArray[i] << endl;
}

// implementations follow...

// implement the Constructor
template <class T>
Array<T>::Array(int size = DefaultSize):
itsSize(size)
{
    pType = new T[size];
    for (int i = 0; i<size; i++)
        pType[i] = 0;
}

// copy constructor
template <class T>
Array<T>::Array(const Array &rhs)
{
    itsSize = rhs.GetSize();
    pType = new T[itsSize];
    for (int i = 0; i<itsSize; i++)
        pType[i] = rhs[i];
}

// operator=
template <class T>
Array<T>& Array<T>::operator=(const Array &rhs)
{
    if (this == &rhs)
        return *this;
    delete [] pType;
    itsSize = rhs.GetSize();
    pType = new T[itsSize];
    for (int i = 0; i<itsSize; i++)
        pType[i] = rhs[i];
    return *this;
}

void main()
{
    bool Stop = false; // flag for looping
    int offset, value;
    Array<int> theArray;

    while (!Stop)
    {
        cout << "Enter an offset (0-9) and a value. (-1 to stop): " ;
        cin >> offset >> value;

        if (offset < 0)
            break;

        if (offset > 9)
        {
            cout << "***Please use values between 0 and 9.***\n";
            continue;
        }

        theArray[offset] = value;
    }

    cout << "\nHere's the entire array:\n";
    cout << theArray << endl;
}

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