VectorBlock< VectorType, Size > Class Template Reference

Expression of a fixed-size or dynamic-size sub-vector. More...

#include <VectorBlock.h>

Inheritance diagram for VectorBlock< VectorType, Size >:

List of all members.

Public Member Functions
	VectorBlock (VectorType &vector, Index start, Index size)
	VectorBlock (VectorType &vector, Index start)
Private Types
enum	{ IsColVector = !(internal::traits<VectorType>::Flags & RowMajorBit) }
typedef Block< VectorType, internal::traits< VectorType > ::Flags &RowMajorBit?1:Size, internal::traits< VectorType > ::Flags &RowMajorBit?Size:1 >	Base

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Detailed Description

template<typename VectorType, int Size>
class VectorBlock< VectorType, Size >

Expression of a fixed-size or dynamic-size sub-vector.

Parameters:

VectorType	the type of the object in which we are taking a sub-vector
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 maniputate 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 <Eigen/Core>
#include <iostream>
using namespace Eigen;
using namespace std;

template<typename Derived>
Eigen::VectorBlock<Derived>
segmentFromRange(MatrixBase<Derived>& v, int start, int end)
{
  return Eigen::VectorBlock<Derived>(v.derived(), start, end-start);
}

template<typename Derived>
const Eigen::VectorBlock<const Derived>
segmentFromRange(const MatrixBase<Derived>& v, int start, int end)
{
  return Eigen::VectorBlock<const Derived>(v.derived(), start, end-start);
}

int main(int, char**)
{
  Matrix<int,1,6> v; v << 1,2,3,4,5,6;
  cout << segmentFromRange(2*v, 2, 4) << endl; // calls the const version
  segmentFromRange(v, 1, 3) *= 5;              // calls the non-const version
  cout << "Now the vector v is:" << endl << v << endl;
  return 0;
}

Output:

Note:

Even though this expression has dynamic size, in the case where 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 <Eigen/Core>
#include <iostream>
using namespace Eigen;
using namespace std;

template<typename Derived>
Eigen::VectorBlock<Derived, 2>
firstTwo(MatrixBase<Derived>& v)
{
  return Eigen::VectorBlock<Derived, 2>(v.derived(), 0);
}

template<typename Derived>
const Eigen::VectorBlock<const Derived, 2>
firstTwo(const MatrixBase<Derived>& v)
{
  return Eigen::VectorBlock<const Derived, 2>(v.derived(), 0);
}

int main(int, char**)
{
  Matrix<int,1,6> v; v << 1,2,3,4,5,6;
  cout << firstTwo(4*v) << endl; // calls the const version
  firstTwo(v) *= 2;              // calls the non-const version
  cout << "Now the vector v is:" << endl << v << endl;
  return 0;
}

Output:

See also:

class Block, DenseBase::segment(Index,Index,Index,Index), DenseBase::segment(Index,Index)

Definition at line 70 of file Core/VectorBlock.h.

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Member Typedef Documentation

template<typename VectorType, int Size>

typedef Block<VectorType, internal::traits<VectorType>::Flags & RowMajorBit ? 1 : Size, internal::traits<VectorType>::Flags & RowMajorBit ? Size : 1> VectorBlock< VectorType, Size >::Base [private]

Reimplemented from Block< VectorType, internal::traits< VectorType >::Flags &RowMajorBit?1:Size, internal::traits< VectorType >::Flags &RowMajorBit?Size:1 >.

Definition at line 77 of file Core/VectorBlock.h.

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Member Enumeration Documentation

template<typename VectorType, int Size>

anonymous enum [private]

Enumerator:

IsColVector

Definition at line 78 of file Core/VectorBlock.h.

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Constructor & Destructor Documentation

template<typename VectorType, int Size>

VectorBlock< VectorType, Size >::VectorBlock	(	VectorType &	vector,
		Index	start,
		Index	size
	)		[inline]

Dynamic-size constructor

Definition at line 88 of file Core/VectorBlock.h.

template<typename VectorType, int Size>

VectorBlock< VectorType, Size >::VectorBlock	(	VectorType &	vector,
		Index	start
	)		[inline]

Fixed-size constructor

Definition at line 98 of file Core/VectorBlock.h.

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The documentation for this class was generated from the following file:

• Core/VectorBlock.h