#ifndef __PBASE_EXPRESSION_TEMPLATE_CLASS_H__
#define __PBASE_EXPRESSION_TEMPLATE_CLASS_H__

template <class A>
struct PExprGen{
	operator const A&() const{
		return *static_cast<const A*>(this);
	}
};

template <class A, class B>
class PAddExpr : public PExprGen<PAddExpr<A,B> >{
	const A& p_a;
	const B& p_b;
	public:
		PAddExpr(const A& a, const B& b) : p_a(a), p_b(b){}
		double operator[](size_t i) const{
			return p_a[i] + p_b[i];
		}
};

template <class A, class B>
inline PAddExpr<A,B> operator + (const PExprGen<A>& a, const PExprGen<B>& b){
	return PAddExpr<A,B>(a,b);
}

template <class A, class B>
class PSubExpr : public PExprGen<PSubExpr<A,B> >{
	const A& p_a;
	const B& p_b;
	public:
		PSubExpr(const A& a, const B& b) : p_a(a), p_b(b){}
		double operator[](size_t i) const{
			return p_a[i] - p_b[i];
		}
};

template <class A, class B>
inline PSubExpr<A,B> operator- (const PExprGen<A>& a, const PExprGen<B>& b){
	return PSubExpr<A,B>(a,b);
}

template <class A>
class PMinusExpr : public PExprGen<PMinusExpr<A> >{
	const A& p_a;
	public:
		PMinusExpr(const A& a) : p_a(a){}
		double operator[](size_t i) const{
			return - p_a[i];
		}
};

template <class A>
inline PMinusExpr<A> operator- (const PExprGen<A>& a){
	return PMinusExpr<A>(a);
}

template <class A>
class PTimesExpr : public PExprGen<PTimesExpr<A> >{
	const A& p_a;
	const double p_b;
	public:
		PTimesExpr(const A& a, double b) : p_a(a), p_b(b){}
		double operator[](size_t i) const{
			return p_a[i]*p_b;
		}
};

template <class A>
inline PTimesExpr<A> operator* (const PExprGen<A>& a, double b){
	return PTimesExpr<A>(a,b);
}

template <class A>
inline PTimesExpr<A> operator* (double b, const PExprGen<A>& a){
	return PTimesExpr<A>(a,b);
}

template <class A>
class PDivExpr : public PExprGen<PDivExpr<A> >{
	const A& p_a;
	const double p_b;
	public:
		PDivExpr(const A& a, double b) : p_a(a), p_b(b){}
		double operator[](size_t i) const{
			return p_a[i]/p_b;
		}
};

template <class A>
inline PDivExpr<A> operator/ (const PExprGen<A>& a, double b){
	return PDivExpr<A>(a,b);
}


#endif