/* -------------------------------------------------------------------
   Unmodular approach to solving a problem:

      Implements Rectangle Rule completely in the MAIN function
   ------------------------------------------------------------------- */

#include <iostream.h>


float f(float x)
{
   return(x*x);
}


int main(int argc, char *argv[])
{
   extern float f(float);

   float  a, b, h, x, integral;
   int    N, i;

   cout << "Enter start of interval: ";
   cin >> a;

   cout << "Enter end of interval: ";
   cin >> b;

   cout << "Enter N (number of segments): ";
   cin >> N;

// -----------------------------------------------------------
// This section implements the Rectangle rule
// vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
   integral = 0.0;
   h = (b-a)/N;
   x = a;

   for (i = 1; i <= N; i = i + 1)
   {  
      integral = integral + f(x)*h;
      x = x + h;
   }
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// This section implements the Rectangle rule
// -----------------------------------------------------------

   cout << "Approximate finite integral = " << integral << "\n";

}