#include "library.h"

// improved

int num_sols_quadratic(double A, double B, double C)
{ const double determinant = B*B - 4*A*C;
  if (determinant > 0)
    return 2;
  if (determinant == 0)
    return 1;
  if (determinant < 0)
    return 0; } 

double solve_quadratic_number(double A, double B, double C, int which)
{ const double determinant = B*B - 4*A*C;
  if (which == 1)
    return (-B - sqrt(determinant)) / (2*A);
  else
    return (-B + sqrt(determinant)) / (2*A); }

double eval_quadratic(double A, double B, double C, double x)
{ return A*x*x + B*x + C; }

double answer_to(string question)
{ print(question);
  return read_double(); }

double difference(double x, double y)
{ if (x < y)
    return y - x;
  else
    return x - y; }

bool close_enough(double a, double b)
{ if (difference(a, b) < 0.0000000001)
    return true;
  else
    return false; }

void evaluate_solution(double x, double y)    
{ print("solution is ");
  print(x);  
  print(" giving ");       
  print(y);
  if (y == 0.0)                  
    print(" perfectly correct\n");
  else if (close_enough(y, 0.0))
    print(" close enough\n");
  else
    print(" WRONG\n"); }

void test_quadratic(double A, double B, double C, int which)
{ const double x = solve_quadratic_number(A, B, C, which);
  double y = eval_quadratic(A, B, C, x);
  evaluate_solution(x, y); }

void test_it()
{ const double A = answer_to("A = ");
  const double B = answer_to("B = ");
  const double C = answer_to("C = ");
  const int num_sols = num_sols_quadratic(A, B, C);
  if (num_sols == 0)
    print("no solutions\n");
  else if (num_sols == 1)
    test_quadratic(A, B, C, 1);
  else
  { test_quadratic(A, B, C, 1);
    test_quadratic(A, B, C, 1); } }

void main()
{ test_it();
  test_it();
  test_it(); }