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Public Types | Public Member Functions | Protected Attributes

Map< PlainObjectType, MapOptions, StrideType > Class Template Reference

A matrix or vector expression mapping an existing array of data. More...

#include <Map.h>

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List of all members.

Public Types

typedef MapBase< MapBase
typedef const Scalar * PointerArgType
typedef Base::PointerType PointerType

Public Member Functions

PointerType cast_to_pointer_type (PointerArgType ptr)
Index innerStride () const
 Map (PointerArgType data, Index size, const StrideType &stride=StrideType())
 Map (PointerArgType data, const StrideType &stride=StrideType())
 Map (PointerArgType data, Index rows, Index cols, const StrideType &stride=StrideType())
Index outerStride () const

Protected Attributes

StrideType m_stride

Detailed Description

template<typename PlainObjectType, int MapOptions, typename StrideType>
class Map< PlainObjectType, MapOptions, StrideType >

A matrix or vector expression mapping an existing array of data.

Parameters:
PlainObjectTypethe equivalent matrix type of the mapped data
MapOptionsspecifies whether the pointer is Aligned, or Unaligned. The default is Unaligned.
StrideTypeoptionnally specifies strides. By default, Map assumes the memory layout of an ordinary, contiguous array. This can be overridden by specifying strides. The type passed here must be a specialization of the Stride template, see examples below.

This class represents a matrix or vector expression mapping an existing array of data. It can be used to let Eigen interface without any overhead with non-Eigen data structures, such as plain C arrays or structures from other libraries. By default, it assumes that the data is laid out contiguously in memory. You can however override this by explicitly specifying inner and outer strides.

Here's an example of simply mapping a contiguous array as a column-major matrix:

Output:

If you need to map non-contiguous arrays, you can do so by specifying strides:

Here's an example of mapping an array as a vector, specifying an inner stride, that is, the pointer increment between two consecutive coefficients. Here, we're specifying the inner stride as a compile-time fixed value.

Output:

Here's an example of mapping an array while specifying an outer stride. Here, since we're mapping as a column-major matrix, 'outer stride' means the pointer increment between two consecutive columns. Here, we're specifying the outer stride as a runtime parameter. Note that here OuterStride<> is a short version of OuterStride<Dynamic> because the default template parameter of OuterStride is Dynamic

Output:

For more details and for an example of specifying both an inner and an outer stride, see class Stride.

Tip: to change the array of data mapped by a Map object, you can use the C++ placement new syntax:

Example:

Output:

This class is the return type of Matrix::Map() but can also be used directly.

See also:
Matrix::Map(), Storage orders

Definition at line 117 of file Map.h.


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

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