/*

* This file is part of the GreasePad distribution (https://github.com/FraunhoferIOSB/GreasePad).

* Copyright (c) 2022-2026 Jochen Meidow, Fraunhofer IOSB

*

* This program is free software: you can redistribute it and/or modify

* it under the terms of the GNU General Public License as published by

* the Free Software Foundation, either version 3 of the License, or

* (at your option) any later version.

*

* This program is distributed in the hope that it will be useful,

* but WITHOUT ANY WARRANTY; without even the implied warranty of

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

* GNU General Public License for more details.

*

* You should have received a copy of the GNU General Public License

* along with this program. If not, see <https://www.gnu.org/licenses/>.

*/

#ifndef FIND_H

#define FIND_H

#include <Eigen/Core>

#include <Eigen/SparseCore>

namespace Matfun {

using Eigen::ArrayXi;

using Eigen::Dynamic;

using Eigen::Index;

using Eigen::Vector;

using Eigen::SparseVector;

//! Find indices of 1-elements in vector

[[nodiscard, maybe_unused]] static ArrayXi

find( const Vector<bool,Dynamic> & cond)

{

ArrayXi idx( cond.count() );

for (int i=0, k=0; i<cond.size(); i++) {

if ( cond(i) ) {

idx(k++) = i;

}

}

return idx;

}

//! Find indices of nonzeros elements in sparse vector

template <typename T>

[[nodiscard]] static Vector<Index,Dynamic>

find( const SparseVector<T> & v)

{

Vector<Index,Dynamic> idx( v.nonZeros() );

Index i=0;

for ( typename SparseVector<T>::InnerIterator it(v); it; ++it) {

idx(i++) = it.index();

}

return idx;

}

} // namespace Matfun

// //! Matlab's find(x,1,'first')

// template <typename T>

// [[nodiscard]] static Index indexOf(const Eigen::Vector<T,Eigen::Dynamic> &v, const T x)

// {

// for ( Index i=0; i<v.size(); i++) {

// if ( v(i)==x ) {

// return i;

// }

// }

// return -1;

//

// /* Eigen 3.4.0

// auto it = std::find( v.begin(), v.end(), i);

// if ( it==v.end() ) {

// return -1;

// }

// return std::distance( v.begin(), it); */

// }

#endif // FIND_H