Errors with ->*

Hello -- long time since I posted on this list.

I'm trying to understand the use of ->* but in compiling the attached 
program which I thought was straightforward I am getting the following 
errors:

foo.cpp: In constructor ‘mystruct::mystruct()’:
foo.cpp:9:12: error: invalid conversion from ‘int*’ to ‘int’
foo.cpp: In function ‘int main()’:
foo.cpp:21:7: error: ‘xptr’ was not declared in this scope
foo.cpp:22:7: error: ‘yptr’ was not declared in this scope

Please help.

-- 
Shriramana Sharma

struct mystruct 
{
public:
	int x, y ;
	int * xptr, yptr ;
	mystruct () 
	{ 
		xptr = & x ; 
		yptr = & y ; 
	}
} ;

int main ( void )
{
	mystruct a ;
	mystruct * aptr = & a ;

	a . x = 1 ; 
	a . y = 2 ;

	a .* xptr = 3 ;
	a .* yptr = 4 ;

	aptr ->* xptr = 5 ;
	aptr ->* yptr = 6 ;
}