/* Return the inner product of two input vectors */

double vl_dot3(
double *v1,       /* Input vector 1  */
double *v2);      /* Input vector 2  */

/* Scale a 3d vector */

void vl_scale3(
double fact,      /* Scale factor  */
double *v1,       /* Input vector  */
double *v2);      /* Output vector */

/* Return length of a 3d vector */

double vl_length3(
double *v1);     /* Vector whose length is desired */

/* Compute the difference of two vectors */
/* v3 = v2 - v1                          */

void vl_diff3(
double *v1,        /*  subtrahend    */
double *v2,        /*  minuend       */
double *v3);       /*  result        */

/* Compute the sum   of      two vectors */
/* v3 = v2 + v1                          */

void vl_sum3(
double *v1,        /*  addend        */
double *v2,        /*  addend        */
double *v3);       /*  result        */

/* Construct a unit vector in direction of input */

void vl_unitvec3(
double *v1,        /* Input vector  */
double *v2);

/* Print a label and the contents of a vector */

void vl_vecprn3(
char *label,
double *vec);