1 // This file is part of Eigen, a lightweight C++ template library
2 // for linear algebra.
3 //
4 // Copyright (C) 2008-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
5 // Copyright (C) 2006-2008 Benoit Jacob <jacob.benoit.1@gmail.com>
6 //
7 // This Source Code Form is subject to the terms of the Mozilla
8 // Public License v. 2.0. If a copy of the MPL was not distributed
9 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
10 
11 #ifndef EIGEN_VECTORBLOCK_H
12 #define EIGEN_VECTORBLOCK_H
13 
14 namespace Eigen {
15 
16 namespace internal {
17 template<typename VectorType, int Size>
18 struct traits<VectorBlock<VectorType, Size> >
19   : public traits<Block<VectorType,
20                      traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
21                      traits<VectorType>::Flags & RowMajorBit ? Size : 1> >
22 {
23 };
24 }
25 
26 /** \class VectorBlock
27   * \ingroup Core_Module
28   *
29   * \brief Expression of a fixed-size or dynamic-size sub-vector
30   *
31   * \tparam VectorType the type of the object in which we are taking a sub-vector
32   * \tparam Size size of the sub-vector we are taking at compile time (optional)
33   *
34   * This class represents an expression of either a fixed-size or dynamic-size sub-vector.
35   * It is the return type of DenseBase::segment(Index,Index) and DenseBase::segment<int>(Index) and
36   * most of the time this is the only way it is used.
37   *
38   * However, if you want to directly maniputate sub-vector expressions,
39   * for instance if you want to write a function returning such an expression, you
40   * will need to use this class.
41   *
42   * Here is an example illustrating the dynamic case:
43   * \include class_VectorBlock.cpp
44   * Output: \verbinclude class_VectorBlock.out
45   *
46   * \note Even though this expression has dynamic size, in the case where \a VectorType
47   * has fixed size, this expression inherits a fixed maximal size which means that evaluating
48   * it does not cause a dynamic memory allocation.
49   *
50   * Here is an example illustrating the fixed-size case:
51   * \include class_FixedVectorBlock.cpp
52   * Output: \verbinclude class_FixedVectorBlock.out
53   *
54   * \sa class Block, DenseBase::segment(Index,Index,Index,Index), DenseBase::segment(Index,Index)
55   */
56 template<typename VectorType, int Size> class VectorBlock
57   : public Block<VectorType,
58                      internal::traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
59                      internal::traits<VectorType>::Flags & RowMajorBit ? Size : 1>
60 {
61     typedef Block<VectorType,
62                      internal::traits<VectorType>::Flags & RowMajorBit ? 1 : Size,
63                      internal::traits<VectorType>::Flags & RowMajorBit ? Size : 1> Base;
64     enum {
65       IsColVector = !(internal::traits<VectorType>::Flags & RowMajorBit)
66     };
67   public:
68     EIGEN_DENSE_PUBLIC_INTERFACE(VectorBlock)
69 
70     using Base::operator=;
71 
72     /** Dynamic-size constructor
73       */
74     EIGEN_DEVICE_FUNC
75     inline VectorBlock(VectorType& vector, Index start, Index size)
76       : Base(vector,
77              IsColVector ? start : 0, IsColVector ? 0 : start,
78              IsColVector ? size  : 1, IsColVector ? 1 : size)
79     {
80       EIGEN_STATIC_ASSERT_VECTOR_ONLY(VectorBlock);
81     }
82 
83     /** Fixed-size constructor
84       */
85     EIGEN_DEVICE_FUNC
86     inline VectorBlock(VectorType& vector, Index start)
87       : Base(vector, IsColVector ? start : 0, IsColVector ? 0 : start)
88     {
89       EIGEN_STATIC_ASSERT_VECTOR_ONLY(VectorBlock);
90     }
91 };
92 
93 
94 } // end namespace Eigen
95 
96 #endif // EIGEN_VECTORBLOCK_H
97