Eigen/src/Core/VectorBlock.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2008-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
// Copyright (C) 2006-2008 Benoit Jacob <jacob.benoit.1@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 EIGEN_VECTORBLOCK_H
#define EIGEN_VECTORBLOCK_H

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

namespace Eigen {

namespace internal {
template <typename VectorType, int Size>
struct traits<VectorBlock<VectorType, Size> >
    : public traits<Block<VectorType, traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
                          traits<VectorType>::Flags & RowMajorBit ? Size : 1> > {};
}  // namespace internal

/** \class VectorBlock
 * \ingroup Core_Module
 *
 * \brief Expression of a fixed-size or dynamic-size sub-vector
 *
 * \tparam VectorType the type of the object in which we are taking a sub-vector
 * \tparam Size size of the sub-vector we are taking at compile time (optional)
 *
 * This class represents an expression of either a fixed-size or dynamic-size sub-vector.
 * It is the return type of DenseBase::segment(Index,Index) and DenseBase::segment<int>(Index) and
 * most of the time this is the only way it is used.
 *
 * However, if you want to directly manipulate sub-vector expressions,
 * for instance if you want to write a function returning such an expression, you
 * will need to use this class.
 *
 * Here is an example illustrating the dynamic case:
 * \include class_VectorBlock.cpp
 * Output: \verbinclude class_VectorBlock.out
 *
 * \note Even though this expression has dynamic size, in the case where \a VectorType
 * has fixed size, this expression inherits a fixed maximal size which means that evaluating
 * it does not cause a dynamic memory allocation.
 *
 * Here is an example illustrating the fixed-size case:
 * \include class_FixedVectorBlock.cpp
 * Output: \verbinclude class_FixedVectorBlock.out
 *
 * \sa class Block, DenseBase::segment(Index,Index,Index,Index), DenseBase::segment(Index,Index)
 */
template <typename VectorType, int Size>
class VectorBlock : public Block<VectorType, internal::traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
                                 internal::traits<VectorType>::Flags & RowMajorBit ? Size : 1> {
  typedef Block<VectorType, internal::traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
                internal::traits<VectorType>::Flags & RowMajorBit ? Size : 1>
      Base;
  enum { IsColVector = !(internal::traits<VectorType>::Flags & RowMajorBit) };

 public:
  EIGEN_DENSE_PUBLIC_INTERFACE(VectorBlock)
  EIGEN_STATIC_ASSERT_VECTOR_ONLY(VectorBlock)
  EIGEN_INHERIT_ASSIGNMENT_OPERATORS(VectorBlock)

  /** Dynamic-size constructor
   */
  EIGEN_DEVICE_FUNC constexpr EIGEN_STRONG_INLINE VectorBlock(VectorType& vector, Index start, Index size)
      : Base(vector, IsColVector ? start : 0, IsColVector ? 0 : start, IsColVector ? size : 1, IsColVector ? 1 : size) {
  }

  /** Fixed-size constructor
   */
  EIGEN_DEVICE_FUNC constexpr EIGEN_STRONG_INLINE VectorBlock(VectorType& vector, Index start)
      : Base(vector, IsColVector ? start : 0, IsColVector ? 0 : start) {}
};

}  // end namespace Eigen

#endif  // EIGEN_VECTORBLOCK_H