question??

[Syk0000000000000@aol.com]

i am taking a class at my high school in c++ and i am using a header file 
called apmatrix.h that my teacher gave to me to write a program. i keep 
getting an illegal structure error whenever i put something simple like this

#include<apmatrix.h>

main()
{
       apmatrix<int> data(20,20,0);
       
       if (data[3,3] == 0)
             data[4,6] = 1;
return 0;
}
it will give me an error in the if statement, well if anyone could possibly 
help me out please do, and thank you.