__vatan2
extern void __vatan2(int, double *, int, double *, int, double *, int);
__vatan2(n, x + 1, stridex, x, stridex, y + 1, stridey);
extern void __vatan2(int, double *, int, double *, int, double *, int);
__vatan2(*n, y, *stridey, x, *stridex, z, *stridez);