Thread: Problem with .CPP program output HELP please!!!

I am a beginner in C++ .i wrote this code in which operator is overloaded on matrices.Go thru the program;

Code:

 :
                                 /*prog.cpp*/
#include<iostream.h>
#include<conio.h>
int k=1;
class matrix
{
	private:
			static int a[20][20];
			int m,n;
	public:
			friend istream& operator>>(istream &cin,matrix&);
			friend ostream& operator<<(ostream &cout,matrix);
			friend matrix operator+(matrix,matrix);
			friend matrix operator-(matrix,matrix);
			friend matrix operator*(matrix,matrix);
			friend matrix operator/(matrix,matrix);
};

istream& operator>>(istream &cin,matrix &a)
{
	int i,j;
	cout<<"Enter the size of the matrix m,n"<<endl;
	cin>>a.m>>a.n;
	cout<<"Enter the matrix"<<endl;
	for(i=0;i<=a.m-1;i++)
	for(j=0;j<=a.n-1;j++)
	  cin>>a.a[i][j];
	return(cin);
}
ostream& operator<<(ostream &cout,matrix a)
{
	int i,j;
	cout<<"The matrix is as follows"<<endl;
	for(i=0;i<=a.m-1;i++)
	{
	  for(j=0;j<=a.n-1;j++)
	   cout<<a.a[i][j]<<"\t";
	  cout<<"\n";
	}
	return(cout);
}
matrix operator+(matrix a,matrix b)
{
	matrix c;
	int i,j;
	c.m=a.m;
	c.n=a.n;
	for(i=0;i<=a.m-1;i++)
	for(j=0;j<=a.n-1;j++)
	c.a[i][j]=a.a[i][j]+b.a[i][j];
	return(c);
}

matrix operator-(matrix a,matrix b)
{
	matrix c;
	int i,j;
	c.m=a.m;
	c.n=a.n;
	for(i=0;i<=a.m-1;i++)
	for(j=0;j<=a.n-1;j++)
	c.a[i][j]=a.a[i][j]-b.a[i][j];
	return(c);
}
matrix operator*(matrix a,matrix b)
{
	matrix c;
	int i,j;
	c.m=a.m;
	c.n=b.n;
	if(a.n==b.m)
	{
	 for(i=0;i<=a.m-1;i++)
	 for(j=0;j<=b.n-1;j++)
	 for(k=0;k<=a.n-1;k++)
	  c.a[i][j]+=a.a[i][k]+b.a[k][j];
	}
	 else
	  k=0;
	return(c);
}
matrix operator/(matrix a,matrix b)
{
	matrix c;
	int i,j;
	c.m=a.m;
	c.n=a.n;
	for(i=0;i<=a.m-1;i++)
	for(j=0;j<=a.n-1;j++)
	c.a[i][j]=(float)a.a[i][j]/float(b.a[i][j]);
	return(c);
}
main()
{
	matrix a,b,c,d,e,f;
	cin>>a>>b;
	c=a+b;
	d=a-b;
	e=a*b;
	f=a/b;
	cout<<"The addition of matrices is:"<<"\n"<<c;
	cout<<"The subtraction of matrices is:"<<"\n"<<d;
	if(k==1)
	cout<<"The multiplication of matrices is:"<<"\n"<<e;
	else
	cout<<"The multiplication of matrices is not possible"<<endl;
	cout<<"The division of matrices is:"<<"\n"<<f;
	getch();
	return(0);
}

When i compile the above prog i get an error :
"Linker error:undefined symbol matrix::a in module prog.cpp"

please help me out with the error.

Why is the member array a static?

Code:

class matrix
{
	private:
			static int a[20][20];

u need to declare static int a[20][20] outside the class and use it directly.

thanks 4 helping me out.The main problem was that a clas cannot have a static member.
thx

A class can have a static member, you just didn't implement it completely. In this case, though, the array shouldn't have been static anyway since each matrix instance should have its own data.