Subj : Returning structures from template classes
To   : borland.public.cpp.borlandcpp
From : DJV
Date : Sat Oct 01 2005 09:38 pm


I am trying to return both a matrix and a simple unsigned integer from a matrix class in a header file to indicate whether a matrix has been successfully inverted.  It occurred to me to use a pointer to a structure, but two problems developed.

1.  In the "main()" body of the calling routine
that calls the matrix class function, 
I do not seem to be able to create a matrix object as part of 
a structure.  I can create a matrix object (or several of 
them if I wish) in the same "main()" body, but only 
by themselves,not as part of a structure.  I can not
assign the matrix size in the structure.  I can
declare a Matrix<complex> q, but not a
Matrix<complex> q(3,3), as I can outside of the structure.

2.  This is a template class, so I do not know the type of data contained in the matrix (complex, int, or double) that is being sent to the template class function.  If I could declare this
structure as a template in the template class, I could simply
return the structure.

3.  I considered creating a pointer to a structure created in the template function after the template data type is received by the function, but I run into problems in the main body of the calling program because the matrix class doesn't seem to work if I incorporate it into a structure, and because I am not sure how to set the pointer to a structure returned by the matrix class equal to a pointer, presumably, to a structure of the same size and containing the same elements in the main calling routine.

Any help would be appreciated.  I realize this may be a bit vague.  My goal is to not return a matrix that is partially inverted but can not be completely inverted, due to the potential to cause the user errors.  I'm using Borland C++ 4.51 to develop the matrix class in a header file.

I have this working if I simply return a matrix.  It seems odd
that I can get the template class to work for sending and
receiving matrices, but am having trouble getting
these matrices incorporated into structures that I can both
send and receive from a template class routine.

Thanks.

.