// eg. We use Tower AOI as an example.
#include "tower_aoi/tower_aoi.h"
#include <cstdio>

// Define map size and visible range
const int kMapWidth = 1024;
const int kMapHeight = 1024;
const int kVisibleRange = 30;

// Define unit enter function
void enter_callback(int me, int other) {
  printf("[unit(%d)] Say: unit(%d) Enter to my range\n", me, other);
}

// Define unit leave function
void leave_callback(int me, int other) {
  printf("[unit(%d)] Say: unit(%d) Leave from my range\n", me, other);
}

void Usage() {
  // You can easily replace TowerAOI with CrossLinkAOI or QuadTreeAOI
  TowerAOI aoi(kMapWidth, kMapHeight, kVisibleRange, enter_callback,
              leave_callback);
  // Add three units, you need your custom numeric id and the coordinate of unit.
  aoi.AddUnit(1, 1, 1);
  aoi.AddUnit(2, 2, 2);
  aoi.AddUnit(3, 3, 3);
  // Update the coordinate of unit.
  aoi.UpdateUnit(1, 1000, 1000);
  aoi.UpdateUnit(1, 1, 1);
  // Remove the unit.
  aoi.RemoveUnit(1);
}

int main(int argc, char const* argv[]) {
  Usage();
  return 0;
}

Output:
[unit(1)] Say: unit(2) Enter to my range
[unit(2)] Say: unit(1) Enter to my range
[unit(2)] Say: unit(3) Enter to my range
[unit(3)] Say: unit(2) Enter to my range
[unit(1)] Say: unit(3) Enter to my range
[unit(3)] Say: unit(1) Enter to my range
[unit(2)] Say: unit(1) Leave from my range
[unit(1)] Say: unit(2) Leave from my range
[unit(3)] Say: unit(1) Leave from my range
[unit(1)] Say: unit(3) Leave from my range
[unit(3)] Say: unit(1) Enter to my range
[unit(1)] Say: unit(3) Enter to my range
[unit(2)] Say: unit(1) Enter to my range
[unit(1)] Say: unit(2) Enter to my range
[unit(2)] Say: unit(1) Leave from my range
[unit(1)] Say: unit(2) Leave from my range
[unit(3)] Say: unit(1) Leave from my range
[unit(1)] Say: unit(3) Leave from my range
[unit(2)] Say: unit(3) Leave from my range
[unit(3)] Say: unit(2) Leave from my range