trouble returning an object by reference
Hello all,
Could anyone tell me why I am losing my object? and possibly how I could correct this problem?
I am having alot of trouble with this function. I would like to return an object by reference from a function, but somewhere between my "return" statement and assigning the result the reference to my returned object gets lost. I don't know why but the destructor is fired by the time I get back inside my assignment operator.
I have tried to include the least amount of code needed to show my problem. Please forgive me for its lengthiness.
Some how after the returning from the operator* and after just entering the assignment (=) operator my returned matrix object is lost. When I go through debugging, the object is still good but is lost before the "if (right.get_length()!=get_length)" statement. I identified this by watching the object.aptr value change from what it was before the return statement. It appears to still be correct when I get to the first line of the assignment operator definition but not after that.
Thanks for any comments.
-fisher
Code:
#include "Matrix.h"
int main(){
matrix<int> MAT(3),MAT2(3);
for (int j=1; j<=3; j++){
for (int i=1; i<=3; i++){
MAT(i,j)=1;
}
}
MAT2=MAT*MAT; //at the moment, this is the troublesome line <---------------------------
return 0;
}
Code:
//Matrix.h
#ifndef MATRIX_H
#define MATRIX_H
#include <iostream>
#include <cstdarg> //for using variable argument functions
template <class T>
class matrix
{
protected:
T *aptr;
int *size; //adjustable array of size of each matrix dimension
int dim; //number of dimensions of matrix
int array_length; //total number of elements in matrix
// array_length=size[0]*size[1]*...*size[dim-2]*size[dim-1]
char type;
public:
// CONSTRUCTOR PROTOTYPES
matrix();//default constructor
matrix(int);// two-dimensional square matrix constructor
matrix(int, int, ...);//an any dimensional matrix
~matrix(){cout<<"matrix distroyed"<<endl;}
//*** --- operators ----***
T &operator()(int, ...);//reference operator: matrix(i,j,...)=matrix[i-1][j-1]...
const matrix &operator= (const matrix &);//assignment operator
//multiplication
const matrix &operator* (matrix &);
};
template <class T>//an any dimensional array
matrix<T>::matrix(int d, int n, ...){
int i;
va_list list;
if(d>0){
dim=d;
size= new int[dim];
size[0]=n;
array_length=n;
va_start(list, n);
for(i=1;i<d;i++){
size[i]=va_arg(list,int);
array_length *= size[i];
}
aptr= new T[array_length];
for (i=0;i<array_length;i++)
aptr[i]=0;
}
va_end(list);
}
template <class T>//reference operator
T &matrix<T>::operator()(int row, ...){
int i, prod=0, element=0;
va_list list;
va_start(list, row);
prod=size[0];
element= (va_arg(list,int)-1)+size[1]*(row-1);
for(i=2;i<dim;i++){
prod*= size[i-1];
element+= prod*(va_arg(list,int)-1);
}
va_end(list);
return aptr[element];
}
template <class T> //assignment operator
const matrix<T> &matrix<T>::operator= (const matrix<T> &right){<------object lost between here
if(&right != this){ //check for self-assignment <-------------------------------------and here
//reallocate memory if different amount of space needed
if( array_length!=right.array_length ){
array_length=right.array_length;
dim=right.dim;
delete [] aptr;
delete [] size;
size= new int[dim];
for(int i=0; i<dim ; i++) size[i]=right.size[i];
aptr= new T[array_length];
}
else{//change size of dimensions if necessary
if(dim!=right.dim){
dim=right.dim;
delete [] size;
size= new int[dim];
}
for(int i=0; i<dim ; i++){
if (size[i]!=right.size[i])
size[i]=right.size[i];
}
}
}
for(int i=0; i<array_length; i++)
aptr[i]=right.aptr[i]; //copy matrix elements
return *this;
}
template<class T>//assumes 2D matrixes
const matrix<T> &matrix<T>::operator* (matrix<T> &right){
T sum;
if((*this).size[1]==right.size[0]){
matrix<T> new_m(2,(*this).size[0],right.size[1]);
//do dot product of rows and columns
// in tensor form Cik=Aij*Bjk (sum over j-index)
for(int i=1;i<=(*this).size[0];i++){
for(int k=1;k<=right.size[1];k++){
sum=0;
for (int j=1; j<=(*this).size[1]; j++){
sum+=(*this)(i,j)*right(j,k);
}
new_m(i,k)=sum;
}
}
return new_m;//this might not be passing back correctly <-----------------------------------
}
}
#endif
