C++ named requirements: LayoutMappingPolicy (since C++23)

 

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LayoutMappingPolicy is a type used to specify layout policy of std::mdspan. It provides a member alias template whose specialization is a LayoutMapping type.

Requirements

A type MP satisfies LayoutMappingPolicy if the type requirements shown below are valid:

Legend

Type	Definition
MP	a layout mapping policy class
M	a layout mapping class
E	a specialization of std::extents

Type requirements

• MP::mapping<E> is valid and denotes a type M that satisfies LayoutMapping.
• M::layout_type is valid and denotes a type MP.
• M::extents_type is valid and denotes a type E.

Standard library

The following standard library types satisfy LayoutMappingPolicy requirements:

layout_left (C++23)	column-major multidimensional array layout mapping policy; leftmost extent has stride 1 (class)
layout_right (C++23)	row-major multidimensional array layout mapping policy; rightmost extent has stride 1 (class)
layout_stride (C++23)	a layout mapping policy with user-defined strides (class)
layout_left_padded (C++26)	column-major layout mapping policy with padding stride that can be greater than or equal to the leftmost extent (class template)
layout_right_padded (C++26)	row-major layout mapping policy with padding stride that can be greater than or equal to the rightmost extent (class template)
Defined in namespace std::linalg
layout_transpose (C++26)	std::mdspan layout mapping policy that swaps the rightmost two indices, extents, and strides of any unique layout mapping policy (class template)
layout_blas_packed (C++26)	std::mdspan layout mapping policy that represents a square matrix that stores only the entries in one triangle, in a packed contiguous format (class template)