// 22.5HV2 Software Engineering II
// Unit 1 Exercise 4

#include <iostream.h>
#include <iomanip.h>
#include <fstream.h>
#include <stdlib.h>  // needed for atoi(), atof()

float poly(float, float, float, float=0, float=0, float=0, float=0);

int main(int argc, char *argv[])
{
   ofstream outs;
   int   i, order;
   float x, coeff[6], x_start, x_end, x_inc;

   if ( argc!=5 ) {
      cerr << "USAGE: ex4 fileout start end inc" << endl;
      return 1;
   }

   outs.open(argv[1]);
   if ( outs.fail() ) {
      cerr << "Error opening " << argv[1] << endl;
      return 1;
   }  

   x_start = atof(argv[2]); 
   x_end = atof(argv[3]); 
   x_inc = atof(argv[4]); 

   cout << "Enter order of polynomial (1-5) : ";
   cin >> order;

   for (i=0;i<=order;i++) {
      cout << "Enter coefficient for power " << i << " : ";
      cin >> coeff[i];
   }

   for (x=x_start;x<x_end;x+=x_inc) {

      outs << x << " ";

      switch (order) {
         case 1: outs << poly(x,coeff[0],coeff[1]);  break;
         case 2: outs << poly(x,coeff[0],coeff[1],coeff[2]); break;
         case 3: outs << poly(x,coeff[0],coeff[1],coeff[2],coeff[3]); break;
         case 4: outs << poly(x,coeff[0],coeff[1],coeff[2],coeff[3],coeff[4]); break;
         case 5: outs << poly(x,coeff[0],coeff[1],coeff[2],coeff[3],coeff[4],coeff[5]); break;
      }

      outs << endl;
   }

   outs.close();
   return 0;
}

float poly(float x, float a, float b, float c=0, float d=0, float e=0, float f=0)
{
   return a + b*x + c*x*x + d*x*x*x + e*x*x*x*x + f*x*x*x*x*x;
}