Why is it saying this...

I have a class called mouse. I'm tring to use the << friend. In my public section of the class declaration I have:

Code:

---

friend ostream & operator << (ostream & o, const mouse m);

---

In the cpp for the definitions I have:

Code:

---

ostream & operator << (ostream & o, const mouse m)
{
    // PRINT MOUSE
    o << "M";

    return o;
}

---

Then I get the error: binary '<<' : no operator defined which takes a right-hand operand of type 'class mouse' (or there is no acceptable conversion)

I'm not sure if you put friend in from of the word ostream but when I tried I got 3 errors, including the first:
'<<' : a friend function can only be declared in a class
'<<' : 'void' function returning a value

Anyone know whats going wrong? If you want I'll post the code, don't think its really nessicary seeing as I'm probably just missing something.

NOMAD

hmm wondering too

I'll post the code for the mouse.h and mouse.cpp, also I have uploaded a zip with mouse.h, mouse.cpp, and main.cpp. assume maze works (cause it does).

PHP Code:

---

#include <iostream>
using std:: ostream;
using std::endl;

#include "maze.h"
//#include "screen.h"

class mouse
{
protected:
    unsigned short x;
    unsigned short y;
    unsigned int steps;
    // N = 1; E = 2; S = 3; W = 4;
    unsigned int direction;
    char footprint;
    bool righthand;

    void turnLeft();
    void turnRight();
    void stepForward();

public:
    mouse(maze<char> m, char charfoot);
    void takeOneStep(maze<char> m);
    bool AmIInTheExit(maze<char> m, unsigned short x, unsigned short y);
    bool AmIInTheEntrance(maze<char> m, unsigned short x, unsigned short y);
    //friend ostream & operator << (ostream & o, const mouse m);
    friend ostream & operator << (ostream & o, const mouse m);

}; 


---

Above is mouse.h

PHP Code:

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#include "mouse.h"

mouse::mouse(maze<char> m, char charfoot)
{    
    m.getEntrance(x, y);
    
    steps = 0;
    // N = 1; E = 2; S = 3; W = 4;
    direction = 2;
    footprint = charfoot;
    righthand = true;
}

void mouse::turnLeft()
{
    direction--;
    if (direction < 1)
        direction = 4;
}

void mouse::turnRight()
{
    direction++;
    if (direction > 4)
        direction = 1;
}

void mouse::stepForward()
{

}

void mouse::takeOneStep(maze<char> m)
{
    //What's the difference between this and stepForward()?
    switch (direction)
    {
    case 1:
        
        if ( !( m.IsThisCellBlocked(x, ( y-1 )) ) )
            y--;
        break;
    case 2:
        if ( !( m.IsThisCellBlocked(( x+1 ), y-1) ) )
            x++;
        break;
    case 3:
        if ( !( m.IsThisCellBlocked(x, ( y+1 )) ) )
            y++;
        break;
    case 4:
        if ( !( m.IsThisCellBlocked(( x-1 ), y-1) ) )
            x--;
        break;
    default:
        break;
    }
}

bool mouse::AmIInTheExit(maze<char> m, unsigned short x, unsigned short y)
{
    return m.IsThisCellTheExit (x, y);
}

bool mouse::AmIInTheEntrance(maze<char> m, unsigned short x, unsigned short y)
{
    return m.IsThisCellTheEntrance (x, y);
}

ostream & operator << (ostream & o, const mouse m)
{

    //Clear screen and set
    //CURSOR AT TOP LEFT!!!
    //ClearScreen();

    // PRINT MOUSE
    cout << "M";

    return o;
}

//End mouse.cpp 


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Above is mouse.cpp

Anyway, hope someone can help cause I'm stumped. I just have a feeling its something stupid so keep your eyes open! :eek:

NOMAD

I sliced out everything that had to do with the maze class, and simply compiled your mouse.cpp and .h with a skeleton main function, and there were no errors (gcc under Linux).

Actually, I just figured out what your problem is =). Its this line:

Code:

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cout << "M";

---

cout isnt defined, because you dont import it from the std namespace. Either #include <iostream.h> instead of #include <iostream> or add:

Code:

---

using std::cout;

---

to the top of the mouse.h file.

It compiled for me because I always use iostream.h, which imports the std namespace.

Z.

I'm sorry, i don't understand you mean:
#include <iostream>
using namespace std;
???

Also, I should have made the cout o right
o << "M";

I'm sorry I'm being so dense. You think you could post the mouse.cpp you got to work?

Thanks once again Z!

NOMAD

Just remove anything that has to do with maze, and change your include to #include <iostream.h>

Z.

Quote:

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Originally posted by Zaei
Just remove anything that has to do with maze, and change your include to #include <iostream.h>

Z.

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Not a good idea.

Not all library vendors have iostream.h importing the new iostreams into the global namespace. In many, it's actually implemented separately.

Therefore, never use iostream.h :)

Ok =).

Z.

I fixed it! Well rather than fixing it I compromised. I turned mouse into a template class and al seems well. Go figure! I tried what you said Z and it worked (compiled) but when I added the maze stuff back it reverted back t how it was. I guess something from maze, maybe its friend ostream, did something.

Anyway, I'm happy it works now!!!:D Thanks Z and everyone else who have helped me!

NOMAD!