//this would be in the enemy classbool isHit(bullet* projectile){ //this ptr used for clarity, not needed if ( this->x == projectile->x && this->y == projectile->y ) {   return true; //collision } return false; //no collisions occured}

//assuming a std::vector of enemies calles "enemies"//and a std::vector of bullets called "bullets"for (std::vector<enemy*>::iterator it = enemies.begin();                                  it != enemies.end();                                  ++it ){  for (std::vector<bullet*>::iterator blt = bullets.begin();                                    blt != bullets.end();                                    ++blt )  {    (*it)->isHit(*blt); //check if bullet hit enemy  }}

#include <allegro.h>#include <vector>   // To use the vector class#include <algorithm>    // To use for_each#include <functional>   // To use mem_fun_ref#include "siheader.h"using namespace std;void init();void deinit();int main() {	init();    vector<Ship> ships;    vector<bullet> bullets;   // Create a new ship and add it to the end of the vector   for (int x=50; x<750; x=x+35) {       for (int y=20; y<200; y=y+35) {           ships.push_back( Ship(x, y) );       }   }    //playervariables   int player_x=400;   int player_y=500;   BITMAP *playerImage;   playerImage = load_bitmap( "test.bmp", NULL);      BITMAP *backGround;   backGround = load_bitmap( "back.bmp", NULL);       	while (!key[KEY_ESC]) {		acquire_screen();		draw_sprite(screen, backGround, 0,0);		if (key[KEY_RIGHT]) {           player_x=player_x+4;        }		if (key[KEY_LEFT]){           if (player_x > 0){              player_x=player_x-4;           }        }		if (key[KEY_SPACE]) {           bullets.push_back( bullet(player_x, player_y) );        }        for (int i = 0; i < ships.size(); i++) {            ships.update();        }        for (int i = 0; i < bullets.size(); i++) {            bullets.update();            bullets.isDestroyed();        }                        for (std::vector<Ship*>::iterator it = ships.begin();                                  it != ships.end();                                  ++it ){  for (std::vector<bullet*>::iterator blt = bullets.begin();                                    blt != bullets.end();                                    ++blt )  {    (*it)->isHit(*blt); //check if bullet hit enemy  }}		//for_each(ships.begin(), ships.end(), mem_fun_ref(&Ship::update));		//for_each(bullets.begin(), bullets.end(), mem_fun_ref(&bullet::update));           //bullets.erase(remove_if(bullets.begin(), bullets.end(), mem_fun_ref(&bullet::isDestroyed)), bullets.end());		rotate_sprite(screen, playerImage, player_x+100, player_y-100, itofix(player_x));				draw_sprite(screen, playerImage, player_x, player_y);	        textout_ex(screen, font, "BLAH", 10, 590,makecol(255, 255, 255), -1);		release_screen();	}	deinit();	return 0;}END_OF_MAIN()void init() {	int depth, res;	allegro_init();	depth = desktop_color_depth();	if (depth == 0) depth = 32;	set_color_depth(depth);	res = set_gfx_mode(GFX_AUTODETECT_WINDOWED, 800, 600, 0, 0);	if (res != 0) {		allegro_message(allegro_error);		exit(-1);	}	install_timer();	install_keyboard();	install_mouse();	/* add other initializations here */}void deinit() {	clear_keybuf();	/* add other deinitializations here */}

class Ship {private:       // We don't want external code to access the coordinates directly   int x, y;public:        // We do want external code to be able to call these functions   // This creates a Ship object with the appropriate coordinates   Ship(int xpos,int ypos) :       x(xpos),  // Sets the ship's x to xpos      y(ypos)   // Sets the ship's y to ypos   {      // No code is currently required here.       // Things may change as your class grows.   }   void update() {      circlefill( screen, x, y, 15, makecol(255,255,255));     if (mouse_b & 1) {        y=y+1;     }        }   bool isHit(bullet* bullet) {      //this ptr used for clarity, not needed      if ( this->x == bullet->x && this->y == bullet->y ) {         return true; //collision      }         return false; //no collisions occured      }};class bullet {private:       // We don't want external code to access the coordinates directly   int x, y;public:        // We do want external code to be able to call these functions   // This creates a Ship object with the appropriate coordinates   bullet(int xpos,int ypos) :       x(xpos),      y(ypos)    {      // No code is currently required here.       // Things may change as your class grows.   }   bool isDestroyed() {       if (y<-10) {          return true;       }       return false;   }   void update() {      circlefill( screen, x, y, 15, makecol(255,255,255));     y=y-5;       //if (y<400) {      //x=0;      //y=0;     //}   }};