chromium/third_party/eigen3/src/Eigen/src/Core/IndexedView.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2017 Gael Guennebaud <[email protected]>
//
// 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 EIGEN_INDEXED_VIEW_H
#define EIGEN_INDEXED_VIEW_H

// IWYU pragma: private
#include "./InternalHeaderCheck.h"

namespace Eigen {

namespace internal {

traits<IndexedView<XprType, RowIndices, ColIndices>>;

template <typename XprType, typename RowIndices, typename ColIndices, typename StorageKind, bool DirectAccess>
class IndexedViewImpl;

}  // namespace internal

/** \class IndexedView
 * \ingroup Core_Module
 *
 * \brief Expression of a non-sequential sub-matrix defined by arbitrary sequences of row and column indices
 *
 * \tparam XprType the type of the expression in which we are taking the intersections of sub-rows and sub-columns
 * \tparam RowIndices the type of the object defining the sequence of row indices
 * \tparam ColIndices the type of the object defining the sequence of column indices
 *
 * This class represents an expression of a sub-matrix (or sub-vector) defined as the intersection
 * of sub-sets of rows and columns, that are themself defined by generic sequences of row indices \f$
 * \{r_0,r_1,..r_{m-1}\} \f$ and column indices \f$ \{c_0,c_1,..c_{n-1} \}\f$. Let \f$ A \f$  be the nested matrix, then
 * the resulting matrix \f$ B \f$ has \c m rows and \c n columns, and its entries are given by: \f$ B(i,j) = A(r_i,c_j)
 * \f$.
 *
 * The \c RowIndices and \c ColIndices types must be compatible with the following API:
 * \code
 * <integral type> operator[](Index) const;
 * Index size() const;
 * \endcode
 *
 * Typical supported types thus include:
 *  - std::vector<int>
 *  - std::valarray<int>
 *  - std::array<int>
 *  - Eigen::ArrayXi
 *  - decltype(ArrayXi::LinSpaced(...))
 *  - Any view/expressions of the previous types
 *  - Eigen::ArithmeticSequence
 *  - Eigen::internal::AllRange     (helper for Eigen::placeholders::all)
 *  - Eigen::internal::SingleRange  (helper for single index)
 *  - etc.
 *
 * In typical usages of %Eigen, this class should never be used directly. It is the return type of
 * DenseBase::operator()(const RowIndices&, const ColIndices&).
 *
 * \sa class Block
 */
template <typename XprType, typename RowIndices, typename ColIndices>
class IndexedView
    : public internal::IndexedViewImpl<XprType, RowIndices, ColIndices, typename internal::traits<XprType>::StorageKind,
                                       (internal::traits<IndexedView<XprType, RowIndices, ColIndices>>::Flags &
                                        DirectAccessBit) != 0> { … };

namespace internal {

// Generic API dispatcher
template <typename XprType, typename RowIndices, typename ColIndices, typename StorageKind, bool DirectAccess>
class IndexedViewImpl : public internal::generic_xpr_base<IndexedView<XprType, RowIndices, ColIndices>>::type { … };

IndexedViewImpl<XprType, RowIndices, ColIndices, StorageKind, true>;

unary_evaluator<IndexedView<ArgType, RowIndices, ColIndices>, IndexBased>;

}  // end namespace internal

}  // end namespace Eigen

#endif  // EIGEN_INDEXED_VIEW_H