C++ (Cpp) Vec2D::subtract示例

void Ship::collide(ew::Collidable const* other) {
  if(dead)
    return;

  Vec2D position = getPosition();

  if(typeid(*other) == typeid(Asteroid)) {
    if(immortalityLeft > 0)
      return;

    Asteroid const* asteroid = static_cast<Asteroid const*>(other);
    if(shape.collidesWith(asteroid->getShape()))
    {
      if(shields <= 0)
      {
        die();
      }
      else
      {
        shields -= 1;
        float speed = asteroid->getVelocity().projection(position.subtract(asteroid->getPosition())).subtract(v).length();
        v = position.subtract(asteroid->getPosition()).uniti().scale(speed);
      }
    }
    return;
  }

  if(typeid(*other) == typeid(UfoLaser)) {
    if(immortalityLeft > 0)
      return;

    UfoLaser const* ufoLaser = static_cast<UfoLaser const*>(other);
    if(shape.collidesWith(ufoLaser->getShape()))
    {
      if(shields <= 0)
      {
        die();
      }
      else
      {
        shields -= 1;
        v += ufoLaser->getVelocity().scale(0.1);
      }
    }
    return;
  }

  if(typeid(*other) == typeid(Ufo)) {
    if(immortalityLeft > 0)
      return;

    Ufo const* ufo = static_cast<Ufo const*>(other);
    if(shape.collidesWith(ufo->getShape()))
    {
      if(shields <= 0)
      {
        die();
      }
      else
      {
        shields -= 1;
      }
    }
    return;
  }

  if(typeid(*other) == typeid(Powerup)) {
    Powerup const* powerup = static_cast<Powerup const*>(other);
    if(powerup->alive() && shape.collidesWith(powerup->getShape()))
    {
      if(powerup->getType() == Powerup::LASER)
      {
        increaseLaserLevel();
      }
      else if(powerup->getType() == Powerup::SPREAD)
      {
        increaseSpreadLevel();
      }
      else if(powerup->getType() == Powerup::BEAM)
      {
        increaseBeamLevel();
      }
      else if(powerup->getType() == Powerup::PLASMA)
      {
        increasePlasmaLevel();
      }
      else if(powerup->getType() == Powerup::EXTRALIFE)
      {
        gameWorld->player.lives += 1;
        new GameNotification(gameWorld, "1up", POWERUP_TEXT_SIZE, 1.0, getPosition());

      }
      else if(powerup->getType() == Powerup::LOSELIFE)
      {
        gameWorld->player.lives -= 1;
        new GameNotification(gameWorld, "-1up", POWERUP_TEXT_SIZE, 1.0, getPosition());

      }
      else if(powerup->getType() == Powerup::SHIELD)
      {
        shields += 1;
        new GameNotification(gameWorld, "Shield +1", POWERUP_TEXT_SIZE, 1.0, getPosition());
      }
    }
    return;
  }
}