PK_VECTOR_t    


struct PK_VECTOR_s
    {
    double coord[3];
    };
typedef struct PK_VECTOR_s PK_VECTOR_t;



This structure represents a 3 space vector.


The components are as follows:

    `coord[0]'  X component of vector
    `coord[1]'  Y component of vector
    `coord[2]'  Z component of vector