/*
 * Tensor2.h
 * @brief Rank 2 Tensor based on http://www.gps.caltech.edu/~walter/FTensor/FTensor.pdf
 * Created on: Feb 10, 2010
 * @author: Frank Dellaert
 */

#pragma once
#include <gtsam/geometry/tensors.h>

namespace tensors {

/** Rank 2 Tensor */
template<int N1, int N2>
class Tensor2 {
protected:
	Tensor1<N1> T[N2];

public:

	/** default constructor */
	Tensor2() {
	}

	/* construct from data */
	Tensor2(const double data[N2][N1]) {
		for (int j = 0; j < N2; j++)
			T[j] = Tensor1<N1> (data[j]);
	}

	/** construct from expression */
	template<class A, char I, char J>
	Tensor2(const Tensor2Expression<A, Index<N1, I> , Index<N2, J> >& a) {
		for (int j = 0; j < N2; j++)
			T[j] = a(j);
	}

	const double & operator()(int i, int j) const {
		return T[j](i);
	}

	double & operator()(int i, int j) {
		return T[j](i);
	}

	/** convert to expression */
	template<char I, char J> Tensor2Expression<Tensor2, Index<N1, I> , Index<
			N2, J> > operator()(Index<N1, I> i, Index<N2, J> j) const {
		return Tensor2Expression<Tensor2, Index<N1, I> , Index<N2, J> > (*this);
	}
};

} // namespace tensors