header

[vanessatse]

[code]
#include <iostream>
#i

[jlb]

Post the error messages exactly as they appear in your development environment.

Also I don't recommend using file names with spaces for your include files.

Is matrix defined in the "Poly header.h" include file?

[vanessatse]

The first

[jlb]

so I'm not sure if it's supported in xcode.

Yes using the #ifndef is supported by any C/C++ compiler.

I've googled around and some say that anything with '_' may be associated with the windows.h header. Is that where the problem is?

No that is not the problem.

The problem is that the linker can't find the implementation for a matrix constructor that takes a matrix parameter.