/* Example 16.2: Pointers to Structures
	Author: Peter Brusilovsky 
*/

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

struct point {
	float x;
	float y;
};

struct point readpoint(char *prompt);
double distance(struct point *p1, struct point *p2);

void main(){
	struct point pbase, p;
	int i;
	
	/* get base point */
	pbase = readpoint("Enter base point");
	
	/* get and check points */
	for (i = 1; i <= 5; ++i) {
		p = readpoint("Enter point");
		printf("Distance from base point is %.2f\n", distance(&pbase, &p));
	} 
}

/* readpoint: reads a point and returns it */
struct point readpoint(char *prompt)
{
	struct point input;
	
	printf("%s (x y):", prompt);
	scanf("%f %f", &(input.x), &(input.y));
	return input;
}
/* distance: returns distance between points */
double distance(struct point *pptr1, struct point *pptr2) {
	double xdiff, ydiff;
	
	xdiff = pptr1->x - pptr2->x; /* same as (*pptr1).x - (*pptr2).x */
	ydiff = pptr1->y - pptr2->y;	
	return(sqrt(xdiff*xdiff + ydiff*ydiff)); 
}