/* Demonstrate usages of pointer type by exmaples of
   a point and a rectangle type in 2D plane
   Emad Arasteh
   December 5 , 2019
*/
#include <stdio.h>

typedef struct
{
  int x;
  int y;
} point_t;

typedef struct
{
  point_t coords[4];
} rectangle_t;

void modify(point_t *p, int v, int w)
{
  p->x = v;
  p->y = w;
}

void display(rectangle_t* rect)
{
  int i;
  printf("Coordinates of the rectangle are:\n");
  for(i = 0; i< 4; i++)
  {
    printf("  (X,Y) : (%d, %d)\n", rect->coords[i].x, rect->coords[i].y);
  }
}

int main()
{
  point_t p1, *p2 = &p1;
  rectangle_t r1 = { { {6, 8}, {6, 14}, {8, 8}, {8, 14} } };
  rectangle_t *r2 = &r1;

  p1.x = 6;
  p1.y = 9;

  printf("P1(X,Y) : (%d, %d)\n", p1.x, p1.y);

  /* 1. pass point_t variable by reference instead of by value */
  modify(p2, 42, 24);

  printf("P1(X,Y) : (%d, %d)\n", p1.x, p1.y);

  /* 2. avoid copying the entire rectangle_t struct by passing only a pointer */
  display(r2);

  return 0;

}