// This file is part of libigl, a simple c++ geometry processing library.
// 
// Copyright (C) 2015 Alec Jacobson <alecjacobson@gmail.com>
// 
// This Source Code Form is subject to the terms of the Mozilla Public License 
// v. 2.0. If a copy of the MPL was not distributed with this file, You can 
// obtain one at http://mozilla.org/MPL/2.0/.
#ifndef SORT_ANGLES_H
#define SORT_ANGLES_H

#include "igl_inline.h"
#include <Eigen/Core>

namespace igl {
    // Sort angles in ascending order in a numerically robust way.
    //
    // Instead of computing angles using atan2(y, x), sort directly on (y, x).
    //
    // Inputs:
    //   M: m by n matrix of scalars. (n >= 2).  Assuming the first column of M
    //      contains values for y, and the second column is x.  Using the rest
    //      of the columns as tie-breaker.
    //   R: an array of m indices.  M.row(R[i]) contains the i-th smallest
    //      angle.
    template<typename DerivedM, typename DerivedR>
    IGL_INLINE void sort_angles(
            const Eigen::PlainObjectBase<DerivedM>& M,
            Eigen::PlainObjectBase<DerivedR>& R);
}

#ifndef IGL_STATIC_LIBRARY
#include "sort_angles.cpp"
#endif

#endif
