/*      program skraatkast 2
 * 
 *      Range of a particle in a uniform gravitational field as a function
 *      of angle. 
 *      Made to investigate what happens, when y_0 is not at ground level.
 *
 *      Input:
 *          x_0, y_0, v_0, g, theta_min, theta_max, theta_step (in degrees)
 *   
 *      Given theta (loop from theta_min to theta_max in theta_step steps)
 *      Calculate t values for which y(t)=0 by solving a 2nd degree equation.
 *      Calculate the corresponding values of x.
 *
 *      Ouput:
 *         theta, t_1, t_2, x_1(t_1),x_2(t_2)
           ..
 *         ..
 *
 *      A plot of x_1(theta) and x_2(theta) will show the optimal angle
 *      and the maximal range.
 * 
 *
 * Author: Peter Snoer Jensen
 * Date: 2019-02-18
 */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char *argv[])
{
    float x_0, y_0, v_0, theta_min, theta_max, theta_step, g;
    float A, B, C, D;
    float theta, theta_rad, t_1, t_2, x_1, x_2;

    if (argc != 8) {
	fprintf(stderr,
		"usage:  %s x_0 y_0 v_0 g theta_min theta_max theta_step\n",
		argv[0]);
	exit(-1);
    }
    sscanf(argv[1], "%f", &x_0);
    sscanf(argv[2], "%f", &y_0);
    sscanf(argv[3], "%f", &v_0);
    sscanf(argv[4], "%f", &g);
    sscanf(argv[5], "%f", &theta_min);
    sscanf(argv[6], "%f", &theta_max);
    sscanf(argv[7], "%f", &theta_step);

    for (theta = theta_min; theta < theta_max; theta += theta_step) {
	theta_rad = theta * M_PI / 180.;
	A = -0.5 * g;
	B = v_0 * sin(theta_rad);
	C = y_0;
	D = B * B - 4. * A * C;
	if (D >= 0) {
	    t_1 = (-B + sqrt(D)) / (2. * A);
	    t_2 = (-B - sqrt(D)) / (2. * A);
	    x_1 = v_0 * cos(theta_rad) * t_1 + x_0;
	    x_2 = v_0 * cos(theta_rad) * t_2 + x_0;
	    fprintf(stdout, "%f %f %f %f %f\n", theta, t_1, t_2, x_1, x_2);
	} else {
	    fprintf(stderr, "D is less than zero at angle %f\n", theta);
	    fprintf(stderr,
		    "Starting below ground level with too little speed are we?\n");
	}
    }
    return 0;
}