/* For copyright information, see olden_v1.0/COPYRIGHT */

#include "defines.h"

/****************************************************************/
/*	Vector Routines.                                        */
/*	From CMU vision library.                                */
/*	They are used only for the VD, not the DT.              */
/* 	They are slow because of large call-by-value parameters.*/
/****************************************************************/

/* V2_cprod: forms triple scalar product of [u,v,k], where k = u cross v */
/* (returns the magnitude of u cross v in space)*/

double V2_cprod(u,v)
 struct VEC2 u,v;
{
    return(u.x * v.y - u.y * v.x);
}


/* V2_dot: vector dot product */

double V2_dot(u,v)
struct VEC2 u,v;
{
    return(u.x * v.x + u.y * v.y);
}

/* V2_times: multiply a vector by a scalar */

struct VEC2 V2_times(c,v)
 double c;
 struct VEC2 v;
{
    struct VEC2 ans;
    ans.x = c * v.x;
    ans.y = c * v.y;
    return(ans);
}

/* V2_sum, V2_sub: Vector addition and subtraction */

struct VEC2 V2_sum(u,v)
 struct VEC2 u,v;
{
    struct VEC2 ans;
    
    ans.x = u.x + v.x;
    ans.y = u.y + v.y;
    return(ans);
}

struct VEC2 V2_sub(u,v)
 struct VEC2 u,v;
{
    struct VEC2 ans;
    ans.x = u.x - v.x;
    ans.y = u.y - v.y;
    return(ans);
}

/* V2_magn: magnitude of vector */

double V2_magn(u)
 struct VEC2 u;
{
    return(sqrt(u.x*u.x+u.y*u.y));
}

/* returns k X v (cross product).  this is a vector perpendicular to v */

struct VEC2 V2_cross(v)
 struct VEC2 v;
{
    struct VEC2 ans;
    ans.x = v.y;
    ans.y = -v.x;
    return(ans);
}