//Excerpt from visionary.C

class nearby_enemy_of {
	const wabbit *const w;
	const unsigned radius;
public:
	nearby_enemy_of(const wabbit *initial_w, int initial_radius)
		: w(initial_w), radius(initial_radius) {}

	bool operator()(const wabbit *other) const throw (terminal::different) {
		return other != w &&
			other->hungry() > w->bitter() &&
			distance(other, w) <= radius;
	}
};