Overloading extraction operator for private two dimensional variable in three dimensional template

helasraizam (18)
I have been having a lot of trouble overriding the extraction operator for my matrices class. The Matrix class is
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template<class T,unsigned int ROWS, unsigned int COLUMNS>
class Matrix
{
public:
    Matrix();
    //blah blah blah
    friend ostream& operator <<(ostream&,const Matrix<T,ROWS,COLUMNS>&);
    //I don't need to make nonpartialize this template function, do I?  If so, how do I do it?
    ~Matrix();
private:
    T* M[ROWS];
}

Then there is the code:
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template<class T,unsigned int H, unsigned int W>
Matrix<T,H,W>::Matrix()			                     // identity matrix
{
	for(int i=0;i<H;i++)
		M[i]=new T[W];
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
			M[i][j]=(i==j)?1:0;
}//this code works JUST FINE
template<class T,unsigned int H,unsigned int W>
Matrix<T,H,W>::~Matrix()
{
	for(int i=0;i<H;i++)
		delete[] M[i];
}
template<class T,unsigned int H,unsigned int W>
ostream& operator<< (ostream& out,const Matrix<T,H,W>& m)

{
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
		{
			char* temp;
			sprintf(temp,"%03d",m.M[i][j]);
			out<<temp;
		}
	return out;
}

Running this, I get the error that m.M is protected, which probably means that I didn't overload the extraction operator properly.
Curiously, I also get the warning
"warning: friend declaration ‘std::ostream& operator<<(std::ostream&, const Matrix<T, ROWS, COLUMNS>&)’ declares a non-template function"
What am I doing wrong?
Last edited on
naraku9333 (2163)
Add the template args to the ostream declaration and implementation.
helasraizam (18)
Do you mean
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...
public:
    Matrix();
    //blah blah blah
    template<class T,unsigned int ROWS,unsigned int COLUMNS>
    friend ostream& operator <<(ostream&,const Matrix<T,ROWS,COLUMNS>&);
...

in which case I get an error for redefining T, ROWS, and COLUMNS,
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...
public:
    Matrix();
    //blah blah blah
    template<class T1,unsigned int ROWS1,unsigned int COLUMNS1>
    friend ostream& operator <<(ostream&,const Matrix<T1,ROWS1,COLUMNS1>&);
...

which also doesn't work (the errors in VC++ and Bluefish don't even match--I prefer Bluefish btw, but I'm stuck with VC++ being at school). Finally, did you mean
 
 
ostream& operator<< <T,H,W>(ostream& out,const Matrix<T,H,W>& m)

which doesn't work whether I put it in the class or the definition of the member?

I've tried as many combinations of the previous three suggestions as I could think of to no avail. If I haven't touched on what you are saying please clarify. Thank you for your reply!
naraku9333 (2163)
AFAIK 
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template<class T,unsigned int ROWS,unsigned int COLUMNS>
    friend ostream& operator <<(ostream&,const Matrix<T,ROWS,COLUMNS>&);
should work. You could also probably simplify this if rather than have the matrix size set as template arg to set them in a ctor.

What are the errors you get?
Last edited on
helasraizam (18)
With the following code:

Matrix.h 
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template <class T, unsigned int ROWS, unsigned int COLUMNS>

class Matrix

{

public:

	Matrix();        									// default constructor

        ~Matrix();        									// destructor
        template<class T,unsigned int ROWS,unsigned int COLUMNS>
	        friend ostream& operator << (ostream&,const Matrix<T,ROWS,COLUMNS>&);
protected:
	T* M[ROWS];

};


Matrix.cpp 
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#include "Matrix.h"


template<class T,unsigned int H, unsigned int W>
Matrix<T,H,W>::Matrix()								// identity matrix
{
	for(int i=0;i<H;i++)
		M[i]=new T[W];
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
			M[i][j]=(i==j)?i+j:0;
}
template<class T,unsigned int H,unsigned int W>
Matrix<T,H,W>::~Matrix()
{
	for(int i=0;i<H;i++)
		delete[] M[i];
}
template<class T,unsigned int H,unsigned int W>
ostream& operator<< (ostream& out,const Matrix<T,H,W>& m)

{
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
		{
			char* temp;
			sprintf(temp,"%03d",m.M[i][j]);
			out<<temp;
		}
	return out;
}


Main.cpp 
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#include "Matrix.cpp"


int main()
{
	cout<<"\nMatrix\n\n";
	
	Matrix<int,3,3> a;
	cout<<a;
	
	cout<<"\n\n";
}


The error is this:

In file included from ./Matrix.cpp:1,
                 from ./Main.cpp:1:
./Matrix.h:16: error: declaration of ‘class T’
./Matrix.h:10: error:  shadows template parm ‘class T’
./Matrix.h:16: error: declaration of ‘unsigned int ROWS’
./Matrix.h:10: error:  shadows template parm ‘unsigned int ROWS’
./Matrix.h:16: error: declaration of ‘unsigned int COLUMNS’
./Matrix.h:10: error:  shadows template parm ‘unsigned int COLUMNS’
./Main.cpp: In function ‘int main()’:
./Main.cpp:9: error: ambiguous overload for ‘operator<<’ in ‘std::cout << a’
./Matrix.cpp:19: note: candidates are: std::ostream& operator<<(std::ostream&, const Matrix<T, H, W>&) [with T = int, unsigned int H = 3u, unsigned int W = 3u]
./Matrix.h:17: note:                 std::ostream& operator<<(std::ostream&, Matrix<T, ROWS, COLUMNS>) [with T = int, unsigned int ROWS = 3u, unsigned int COLUMNS = 3u, T = int, unsigned int ROWS = 3u, unsigned int COLUMNS = 3u]


As for ctoring the dimensions--I want them to be definite and I want to force the user to set them upon initialization--can I do that in ctor? I think I need ctor() before I can have ctor(int rows,int columns).

Thanks again for your quick replies!
naraku9333 (2163)
Everything should be in the header with templates.
helasraizam (18)
The initializers work, so you must mean the extraction operator--but it must be a nonmember friendly class since we can't overwrite it directly. Do you mean I should move lines 19-35 of Main.cpp into Matrix.h? I will try it but I don't think it will work since we are overloading a member of another class. Or have I misunderstood?
naraku9333 (2163)
No sorry, I mean everything in Matrix.cpp should be in Matrix.h. So youll have the following

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template <class T, unsigned int ROWS, unsigned int COLUMNS>

class Matrix

{

public:

	Matrix();        									// default constructor

        ~Matrix();        									// destructor
        template<class T,unsigned int ROWS,unsigned int COLUMNS>
	        friend ostream& operator << (ostream&,const Matrix<T,ROWS,COLUMNS>&);
protected:
	T* M[ROWS];

};

template<class T,unsigned int H, unsigned int W>
Matrix<T,H,W>::Matrix()								// identity matrix
{
	for(int i=0;i<H;i++)
		M[i]=new T[W];
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
			M[i][j]=(i==j)?i+j:0;
}
template<class T,unsigned int H,unsigned int W>
Matrix<T,H,W>::~Matrix()
{
	for(int i=0;i<H;i++)
		delete[] M[i];
}
template<class T,unsigned int H,unsigned int W>
ostream& operator<< (ostream& out,const Matrix<T,H,W>& m)

{
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
		{
			char* temp;
			sprintf(temp,"%03d",m.M[i][j]);
			out<<temp;
		}
	return out;
}
helasraizam (18)
This is curious; in class we put it in the declarations in an h file and the code in a cpp file.
The following code
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#pragma once


#include <string>

#include <iostream>
#include <cmath>
#include <cstdio>

using namespace std;


template <class T, unsigned int ROWS, unsigned int COLUMNS>

class Matrix

{

public:

	Matrix();        									// default constructor

	~Matrix();        									// destructor
	template<class T,unsigned int ROWS,unsigned int COLUMNS>
	friend ostream& operator << (ostream&,const Matrix<T,ROWS,COLUMNS>&);
protected:
	T* M[ROWS];

};


template<class T,unsigned int H, unsigned int W>
Matrix<T,H,W>::Matrix()								// identity matrix
{
	for(int i=0;i<H;i++)
		M[i]=new T[W];
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
			M[i][j]=(i==j)?i+j:0;
}
template<class T,unsigned int H,unsigned int W>
Matrix<T,H,W>::~Matrix()
{
	for(int i=0;i<H;i++)
		delete[] M[i];
}
template<class T,unsigned int H,unsigned int W>
ostream& operator<< (ostream& out,const Matrix<T,H,W>& m)

{
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
		{
			char* temp;
			sprintf(temp,"%03d",m.M[i][j]);
			out<<temp;
		}
	return out;
}

gives the errors

In file included from ./Main.cpp:1:
./Matrix.h:16: error: declaration of ‘class T’
./Matrix.h:10: error: shadows template parm ‘class T’
./Matrix.h:16: error: declaration of ‘unsigned int ROWS’
./Matrix.h:10: error: shadows template parm ‘unsigned int ROWS’
./Matrix.h:16: error: declaration of ‘unsigned int COLUMNS’
./Matrix.h:10: error: shadows template parm ‘unsigned int COLUMNS’


So I tried removing the bold:
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        template<class T,unsigned int ROWS,unsigned int COLUMNS>
	        friend ostream& operator << (ostream&,const Matrix<T,ROWS,COLUMNS>&);

and got a stream of much more interesting errors

In file included from ./Main.cpp:1:
./Matrix.h:16: warning: friend declaration ‘std::ostream& operator<<(std::ostream&, const Matrix<T, ROWS, COLUMNS>&)’ declares a non-template function
./Matrix.h:16: note: (if this is not what you intended, make sure the function template has already been declared and add <> after the function name here)
/tmp/ccLbNKsK.o: In function `main':
Main.cpp:(.text+0x3b): undefined reference to `operator<<(std::basic_ostream<char, std::char_traits<char> >&, Matrix<int, 3u, 3u> const&)'
collect2: ld returned 1 exit status

I think your code should stay lol
But what do I do about the errors?

In file included from ./Main.cpp:1:
./Matrix.h:16: error: declaration of ‘class T’
./Matrix.h:10: error: shadows template parm ‘class T’
./Matrix.h:16: error: declaration of ‘unsigned int ROWS’
./Matrix.h:10: error: shadows template parm ‘unsigned int ROWS’
./Matrix.h:16: error: declaration of ‘unsigned int COLUMNS’
./Matrix.h:10: error: shadows template parm ‘unsigned int COLUMNS’

I just got really excited when g++ compiled
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#pragma once


#include <string>

#include <iostream>
#include <cmath>
#include <cstdio>

using namespace std;


template <class T, unsigned int ROWS, unsigned int COLUMNS>

class Matrix

{

public:

	Matrix();        									// default constructor

	~Matrix();        									// destructor
	template<class T1,unsigned int ROWS1,unsigned int COLUMNS1>
	friend ostream& operator << (ostream&,const Matrix<T1,ROWS1,COLUMNS1>&);
protected:
	T* M[ROWS];

};


template<class T,unsigned int H, unsigned int W>
Matrix<T,H,W>::Matrix()								// identity matrix
{
	for(int i=0;i<H;i++)
		M[i]=new T[W];
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
			M[i][j]=(i==j)?i+j:0;
}
template<class T,unsigned int H,unsigned int W>
Matrix<T,H,W>::~Matrix()
{
	for(int i=0;i<H;i++)
		delete[] M[i];
}
template<class T,unsigned int H,unsigned int W>
ostream& operator<< (ostream& out,const Matrix<T,H,W>& m)

{
	for(int i=0;i<H;i++)
		for(int j=0;j<W;j++)
		{
			char* temp;
			sprintf(temp,"%03d",m.M[i][j]);
			out<<temp;
		}
	return out;
}

(changed parts in bold) but the output is

Matrix

Segmentation fault

hmph :/
naraku9333 (2163)
char* temp
In your extraction operator overload doesn't point to any memory.
helasraizam (18)
THAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAANK YOUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU!!!!!!!
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