/* Define a struct to describe a point in the 2D plane,
   modify the coordinate using pointer and find perimeter of an arbitrary triangle
   Emad Arasteh
   December 6, 2018
*/

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

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

void display(point_t p) {
  printf("(x, y) coordinate is (%d, %d) \n", p.x, p.y);
}

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

double perimeter(const point_t vertices[]) {
  double perimeter = 0;
  int i;
  for (i = 0; i < 2; i++) {
    perimeter += sqrt(pow(vertices[i+1].x - vertices[i].x, 2) + pow(vertices[i+1].y - vertices[i].y, 2));
  }
  return perimeter;
}


int main() {
  point_t  p1;
  point_t* p2;
  point_t  tri[3] = { {0, 0}, {6, 0}, {6, 8}} ; /* vertices of an arbitrary triangle */
  int      i;

  p1.x = 76;
  p1.y = 10;

  p2 = &p1;

  display(p1);
  modify(p2, 42, 42);
  display(p1);

  printf("Vertices of a triangle has the following coordinates: \n");
  for(i = 0; i < 3; i++) {
    display(tri[i]);
  }

  printf("Perimter of the triangle is %f \n", perimeter(tri));
  return 0;
}