#include <assert.h>
#include "output.h"

void line(int x0, int y0, int x1, int y1) 
{
  int x = x0;
  int y = y0;
  int a = x1 - x0;
  int b = y1 - y0;
  int d = 0;			/* d = a * (y-y0) - b * (x-x0)*/
  /* Check preconditions */
  assert(a >= 0);
  assert(b >= 0);
  assert(b <= a);
  /* End of check of preconditions */
  output(x, y);
  while(x < x1) {
    x += 1;
    d -= b;
    if(2*d < -a) {
      y += 1;
      d += a;
    }
    output(x, y);
  }
}