#include <stdio.h>
#include <math.h>

/*
 * static.c -- demonstrates the use static variables in a function
 */

// forward declaration
double dist ( double x, double y );

int main ( int argc, char *argv[] )
{
   /* Call dist() with new coordinates to get new drift distance
    * Old coordinates will be managed by dist() function through static variables.
    */
   printf("drift: %g\n", dist(1.0, 1.0));
   printf("drift: %g\n", dist(1.0, 2.0));
   printf("drift: %g\n", dist(2.0, 2.0));
   printf("drift: %g\n", dist(0.0, 0.0));

   return 0;
}

double dist ( double x, double y )
{
   static double ox = 0.0;
   static double oy = 0.0;

   double d, dx, dy;

   dx = x - ox; 
   dy = y - oy; 

   d = sqrt ( dx * dx + dy * dy );

   ox = x; 
   oy = y; 

   return d;
}