/*
 * Program to find real roots of quadratic equation, using a function with 
 * pointer arguments.
 * 
 * FIXME -- need to figure out printing, error checking
 */
#include <stdio.h>
#include <math.h>

/* 
 * returns:
 * how many roots were found, unless special case of a, b, c, all zero,
 * then -1
 */
int find_real_roots(double a, double b, double c, double *r1, double *r2);

void print_solution(int root_return_value, double r1, double r2);

/* 
 * FIXME add this?
 * calculate roots and print 
void test(double a, double b, double c);
 */

int main(void) {
	/* FIXME test cases from previous version
	print_real_roots(1, 0, -1);
	print_real_roots(1, -4, 4);
	print_real_roots(1, 0, 1);
	print_real_roots(0, 2, 1);
	print_real_roots(0, 0, 1);
	print_real_roots(0, 0, 0);
	*/

	printf("enter coefficients a, b, c\n");
	double a, b, c;
	if (scanf("%lf %lf %lf", &a, &b, &c) != 3) {
		printf("invalid input\n");
		return 1; /* bail out of program */
	}

	double r1, r2;
	int r = find_real_roots(a, b, c, &r1, &r2);
	printf("a = %f, b = %f, c = %f\n", a, b, c);
	print_solution(r, r1, r2);
	return 0;
}

int find_real_roots(double a, double b, double c, double *r1, double *r2) {
	double d = b*b - 4*a*c;
	if (d < 0) {
		return 0;
	} 

	if (a != 0) {
		*r1 = (-b + sqrt(d))/(2*a);
		*r2 = (-b - sqrt(d))/(2*a);
		return 2;
	} else if (b != 0) {
		*r1 = -c / b;
		*r2 = *r1;
		return 1;
	} else {
		if (c != 0) {
			return 0;
		} else {
			return -1;
		}
	}
}

void print_solution(int root_return_value, double r1, double r2) {
	switch (root_return_value) {
		case 2:
			printf("two roots %f %f\n", r1, r2);
			break;
		case 1:
			printf("one root %f\n", r1);
			break;
		case 0:
			printf("no (real) solutions\n");
			break;
		case -1:
			printf("everything a solution!\n");
			break;
		default:
			printf("should not happen!\n");
	}
}