// a point in 2 dimensions
//
typedef struct { double x, y; } Point;

// functions from point.c
//
void print(const char msg[], Point p);
double distance( Point p, Point q);
// a point in 2 dimensions
//
#include <stdio.h>
#include <math.h>
// #include "point.h"

void print(const char msg[], Point p)
{ 
  printf( "%s: (%g,%g)\n", msg, p.x, p.y);
}

double distance( Point p, Point q)
{
  double dx = p.x - q.x, dy = p.y - q.y;

  return sqrt(dx*dx+dy*dy);
}
// 2D point example
//
#include <stdio.h>
// #include "point.h"

int main( void)
{
  Point p = { 1, 2 }, q = { 3, 4}; 

  print("p",p); print("q",q);

  printf( "distance = %g\n", distance(p,q) );
}