#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <string.h>
#include <math.h> 
#define MIN_DEFAULT -100
#define MAX_DEFAULT 100
#define STEP_DEFAULT 0.1

using namespace std;
double equ(double x,double a, double b, double c){
  return a*x*x+b*x+c;
}

//quadratic equation 1
int main(int argc, char *argv[] ){
  double a,b,c;
  double min,max,step;
  double x,y,y_pre;
  double ans[16];
  int i;
  int ans_num=0;
  if(argc<4){
    cerr<< "quadra_1 a b c min max step"<< endl;
    return 1;
      }
  else{
    a=atof(argv[1]);
    b=atof(argv[2]);
    c=atof(argv[3]);
  }
  if(argc<6){
    min=MIN_DEFAULT;
    max=MAX_DEFAULT;
  }
  else{
    min=atof(argv[4]);
    max=atof(argv[5]);
  }
  if(argc<7){
    step=STEP_DEFAULT;
  }  
  else{
    step=atof(argv[6]);
  }

  // output the parameters
  cerr << "quadra_1 for solving quadratic equation"<<endl;
  cerr <<"equation: "<<a<<"*x^2 + "<< b << "*x + " << c << " = 0"<<endl;
  cerr <<"ans search range: "<<min<<" : "<< max  << " (step= " << step << ")"<<endl<<endl;

  //initialization
  x=min;
  y_pre=equ(x,a,b,c);

  //answer search
  while(x<max){
    y=equ(x,a,b,c);
    if(y==0){
      cerr << "exact answer candidate found: "<<x<<endl; 
      cerr << "\t\t y="<<y <<endl;
      ans[ans_num]=x;
      ans_num++;
    }
    else if(y*y_pre<0){
      cerr << "answer candidate found in "<<x-step<<" " <<x<<endl; 
      cerr << "\t\t y="<<y_pre<<" : " <<y <<endl;
      ans[ans_num]=x-step/2;
      ans_num++;
    }
    y_pre=y;
    x+=step;
  }
  for(i=0;i<ans_num;i++){
    cerr<<"y("<<ans[i]<<")="<<equ(ans[i],a,b,c)<<endl;
  }

}