100vector.c

// Isaac Haseley - Nathan Mannes - CS311 - Winter 2017

/*** In general dimensions ***/

/* Copies the dim-dimensional vector v to the dim-dimensional vector copy. */
void vecCopy(int dim, double v[], double copy[]) {
	for (int i = 0; i < dim; i++) {
		copy[i] = v[i];
	}
}

/* Adds the dim-dimensional vectors v and w. */
void vecAdd(int dim, double v[], double w[], double vPlusW[]) {
	for (int i = 0; i < dim; i++) {
		vPlusW[i] = v[i] + w[i];
	}
}

/* Subtracts the dim-dimensional vectors v and w. */
void vecSubtract(int dim, double v[], double w[], double vMinusW[]) {
	for (int i = 0; i < dim; i++) {
		vMinusW[i] = v[i] - w[i];
	}
}

/* Scales the dim-dimensional vector w by the number c. */
void vecScale(int dim, double c, double w[], double cTimesW[]) {
	for (int i = 0; i < dim; i++) {
		cTimesW[i] = c * w[i];
	}
}

/* Assumes that there are dim + 2 arguments, the last dim of which are doubles. 
Sets the dim-dimensional vector v to those doubles. */
void vecSet(int dim, double v[], ...) {
    va_list argumentPointer;
    va_start(argumentPointer, v);
    for (int i = 0; i < dim; i++) {
        v[i] = va_arg(argumentPointer, double);
    }
    va_end(argumentPointer);
}

/* Returns the dot product of the dim-dimensional vectors v and w. */
double vecDot(int dim, double v[], double w[]) {
    int i;
    double answer = 0;
    for(i = 0; i < dim; i++) {
        answer += v[i] * w[i];
    }
    return answer;
}

/* Returns the length of the dim-dimensional vector v. */
double vecLength(int dim, double v[]) {
    double x = vecDot(dim, v, v);
    return sqrt(x);
}

/* Returns the length of the dim-dimensional vector v. If the length is 
non-zero, then also places a scaled version of v into the dim-dimensional 
vector unit, so that unit has length 1. */
double vecUnit(int dim, double v[], double unit[]) {
    double x = vecLength(dim, v);
    if (x != 0) {
        vecScale(dim, 1/x, v, unit);    
    }
    return x;
}
/* Computes the cross product of the 3-dimensional vectors v and w, and places 
it into vCrossW. */
void vec3Cross(double v[3], double w[3], double vCrossW[3]) {
    vCrossW[0] = v[1] * w[2] - w[1] * v[2];
    vCrossW[1] = w[0] * v[2] - v[0] * w[2];
    vCrossW[2] = v[0] * w[1] - w[0] * v[1];    
}

/* Computes the 3-dimensional vector v from its spherical coordinates. 
rho >= 0.0 is the radius. 0 <= phi <= pi is the co-latitude. -pi <= theta <= pi 
is the longitude or azimuth. */
void vec3Spherical(double rho, double phi, double theta, double v[3]) {
    v[0] = rho * sin(phi) * cos(theta);
    v[1] = rho * sin(phi) * sin(theta);
    v[2] = rho * cos(phi);    
}