#include <stdio.h>

struct point {
  double x, y;
};

typedef struct point point;

struct quadrangle {
  int rank;
  struct point points[4];
};

typedef struct quadrangle quadrangle;

quadrangle make_quadrangle(point corners[]){
  int i;
  struct quadrangle result;

  result.rank = 4;
  for(i = 0; i < 4; i++)
    result.points[i] = corners[i];

  return result;
}

int main(void) {
  quadrangle
     q1 = {4, {{1.0, 1.0}, {7.0, 7.0}, {-5.0, 0.0}, {-15.0, 16.0}}}, 
     q2;
  point corner_points[] = { {1.0, 1.0}, {7.0, 7.0}, {-5.0, -5.0}, {5.0, -16.0} };

  q2 = make_quadrangle(corner_points);

  // ...

  printf("Size of quadrangle: %d bytes\n", sizeof(quadrangle));
  
  return 0;
}