bind gives error C2065: '_1' : undeclared identifier

[strawberry]

Trying to make one of the programs in "Efficient C++" work:

#include<iostream>
#include<functional>

class GameCharacter; // forward declaration

int defaultHealthCalc(const GameCharacter& gc) {
	return 10;
}

class GameCharacter{ // Base class
public:
	typedef std::tr1::function<int (const GameCharacter&)> HealthCalcFunc; 
	explicit GameCharacter(HealthCalcFunc hcf = defaultHealthCalc)  :healthFunc(hcf){} // constructor
	void setHealthFunction(HealthCalcFunc hcf){ // resets object's health calculator
		healthFunc = hcf;
	}
	int healthValue() const { // non-virtual fn, derived classes inherit this 
		return healthFunc(*this);
	}
private:
	HealthCalcFunc healthFunc; // pointer to function
};

class EvilBadGuy : public GameCharacter{
public:
	explicit EvilBadGuy(HealthCalcFunc hcf = defaultHealthCalc) : GameCharacter(hcf) {} // constructor
};
class GameLevel{
public:
	GameLevel(int l = 1) : level(l){}
	int health(const GameCharacter& gc) const {
		return level * 10000;
	}
	void setLevel(int l) {
		level = l;
	}
private:
	int level;
};

int main(){
	GameLevel currentLevel; // default construct 
	EvilBadGuy ebg3(std::tr1::bind(&GameLevel::health, std::tr1::cref(currentLevel),_1)); 
	std::cout << ebg3.healthValue() << std::endl;

	return 0;
}

The "bind" gives the error in the title though it seems it should work based on the book.

[PanGalactic]

With g++, I have to add the following:

#include <tr1/functional>

using namespace std::tr1::placeholders;

You probably just need the second line.

[strawberry]

The second line helped. -Thanks.