#include <stdio.h>

#define PI 3.14159265

/* Define a structure named point - and define a type named "point" which
** is the same as "struct point"
*/
typedef struct point 
{
    int x;
    int y;
} point;

/* We don't need to name the structure when using a typedef */
typedef struct 
{
    point ll;	/* lower left */
    point ur;	/* upper right */
} rectangle;

struct circ 
{
    point centre;
    int radius;
};
/* The typedef can be separated from the structure definition and need 
** not have the same name*/
typedef struct circ circle;
	
	
/* Function prototypes */
void make_point(point* p, int x, int y);
void make_rectangle(rectangle* r, point lower_left, point upper_right);
int rectangle_area(rectangle r);	
double circle_area(circle c);		

int is_square(rectangle r);


int main() 
{
    /* It is possible to initialise structures when they are created (in a 
    ** similar fashion to the way arrays can be initialised). We can refer 
    ** to points as "point" or "struct point" */
    point a = {1, -1};
    struct point b = {5, 3};
    point p;
    rectangle r1 = { {2, 2}, {5,6} };
    rectangle r2;
    circle c1;
    
    make_point(&p, -1, -1);	/* Modified the way this is called */
    c1.centre = p; /* Structures can be copied */
    c1.radius = 4;
    
    make_rectangle(&r2, a, b);	/* Modified the way this is called */
    printf("Rectangle 1: (%d,%d) to (%d,%d). Area is %d\n", 
	    r1.ll.x, r1.ll.y, r1.ur.x, r1.ur.y, rectangle_area(r1));
    printf("Rectangle 2: (%d,%d) to (%d,%d). Area is %d\n", 
	    r2.ll.x, r2.ll.y, r2.ur.x, r2.ur.y, rectangle_area(r2));
    printf("Circle: centred at (%d,%d), radius %d. Area is %g\n",
	    c1.centre.x, c1.centre.y, c1.radius, circle_area(c1));

}

void make_point(point *p, int x, int y) 
{
    p->x = x;
    p->y = y;
}

void make_rectangle(rectangle *r, point ll, point ur) 
{
    r->ll = ll;
    r->ur = ur;
}

int rectangle_area(rectangle r) 
{
    return (r.ur.y - r.ll.y) * (r.ur.x - r.ll.x);
}

double circle_area(circle c) 
{
    /* Note that because we multiply integers by a double, the result will 
    ** be a double */
    return (PI * c.radius * c.radius);
}