porting error I don't understand

[mark]

Hi,

recently I revisited some code I wrote a few years ago using the
Borland c++ 3.0 compiler. I'm in the middle of porting the code to g++
{gcc version 3.3.4 (pre 3.3.5 20040809)} and I'm stuck with a specific
error I just don't seem to understand.

The error I get is:

mchpoly.cpp: In function `Vector CharacteristicPolynom(Matrix&)':
mchpoly.cpp:71: error: no match for 'operator=' in 'Y =
ProductMatrix(Matrix&,
   Matrix&)((&Y))'
matrix.h:142: error: candidates are: Matrix& Matrix::operator=(Matrix&)

The corresponding line is:

 ...
 ...
 ...

 do {
     for( R = 1; R <= N; R++ )    /* create random Y0 */
      VectorElement( Y, R ) = complex( rand() % 10, rand() % 10 );

     for( R = 1; R <= N; R++ )     /* for each row ... */
     {
      for( C = 1; C <= N; C++ )      /* add Yn to T */
       MatrixElement( T, C, N - R + 1 ) = VectorElement( Y, C );

=====>>>>      Y = ProductMatrix( M, Y );         /* calculate new Yn
*/
     }

     DoGaussJordan( T, Y );          /* solve the equation into Y */
     I--;
    } while( ( MatrixElement( T, N, N ) != ONE_CMPLX ) && ( I ) );

 ...
 ...
 ...


The definition of the ProductMatrix function is:

Matrix ProductMatrix( Matrix& A, Matrix& B )
{
 Matrix Prod;
 unsigned R, C, k;
 unsigned PR, PC, AC;

 ...
 ...
 ...

 return( Prod );
}

Moreover, the class definition of Matrix contains:

class Matrix { public:                      /* def of a matrix */

               // constructors
               Matrix( void );

 ...
 ...
 ...
               // overloaded operators
               Matrix&  operator=( Matrix& A );

 ...
 ...
 ...

}


The reason why in operator= the A matrix is passed as a reference is
because the operator= is used to "pass-through" memory from A to *this
by copying a pointer. In A however, the pointer should be set to 0 (or
NULL) in order to make sure that the calling of the destructor of A
doesn't free the memory. So in short the operator= changes Matrix *this
as well as Matrix A.

As far as I understand, the compiler is not able to find a correct
operator= function, yet I think I've defined and implemented one.
Moreover, I've noticed that the function reference in the error
contains an "((&Y))" part, something I didn't expect. What's the deal
with that?

Could anyone give a clue on this?

As a side note: the code compiled fine of course with Borland, Cray and
MIPS c++ compilers three years ago. It doesn't however with g++ and the
newly available Intel C++ compiler.

best regards, 

mark somers.