Support functions swich between array indices and flat indices

Enumerations
enum class	xt::stride_type { xt::stride_type::internal = 0 , xt::stride_type::normal = 1 , xt::stride_type::bytes = 2 }
	Choose stride type. More...

Functions
template<class offset_type, class S, class Arg, class... Args>
offset_type	xt::data_offset (const S &strides, Arg arg, Args... args) noexcept
	Return the flat index for an array index.
template<layout_type L = layout_type::dynamic, class shape_type, class strides_type>
std::size_t	xt::compute_strides (const shape_type &shape, layout_type l, strides_type &strides)
	Compute the strides given the shape and the layout of an array.
template<class S, class... Args>
void	xt::normalize_periodic (const S &shape, Args &... args)
	Normalise an index of a periodic array.
template<class E>
auto	xt::strides (const E &e, stride_type type=stride_type::normal) noexcept
	Get strides of an object.
template<class E>
auto	xt::strides (const E &e, std::size_t axis, stride_type type=stride_type::normal) noexcept
	Get stride of an object along an axis.

Detailed Description

Enumeration Type Documentation

stride_type

enum class xt::stride_type

strong

Choose stride type.

Enumerator
internal	As used internally (with stride(axis) == 0 if shape(axis) == 1)
normal	Normal stride corresponding to storage.
bytes	Normal stride in bytes.

Definition at line 233 of file xstrides.hpp.

Function Documentation

compute_strides()

template<layout_type L = layout_type::dynamic, class shape_type, class strides_type>

std::size_t xt::compute_strides ( const shape_type & shape, layout_type l, strides_type & strides )

inline

Compute the strides given the shape and the layout of an array.

Parameters

shape	Shape of the array.
l	Layout type, see xt::layout_type().
strides	(output) Strides of the array.

Returns

The size: the product of the shape.

Definition at line 566 of file xstrides.hpp.

data_offset()

template<class offset_type, class S, class Arg, class... Args>

offset_type xt::data_offset ( const S & strides, Arg arg, Args... args )

inlinenoexcept

Return the flat index for an array index.

Given m arguments, and dimension nof the array (n == strides.size()).

• If m == n, the index is strides[0] * index[0] + ... + strides[n - 1] * index[n - 1].
• If m < n and the last argument is xt::missing the indices are zero-padded at the end to match the dimension of the array. The index is then strides[0] * index[0] + ... + strides[m - 1] * index[m - 1].
• If m < n (and the last argument is not xt::missing), the index is strides[n - m - 1] * index[0] + ... + strides[n - 1] * index[m - 1].
• If m > n, then the first m - n arguments are ignored. The index is then strides[0] * index[m - n] + ... + strides[n - 1] * index[m - 1].

Parameters

strides	Strides of the array.
args	Array index.

Returns

The flat index.

Definition at line 453 of file xstrides.hpp.

normalize_periodic()

template<class S, class... Args>

void xt::normalize_periodic ( const S & shape, Args &... args )

inline

Normalise an index of a periodic array.

For example if the shape is (3, 4) and the index is (3, -4) the result is (0, 0).

Parameters

shape	Shape of the array.
args	(input/output) Array index.

Definition at line 909 of file xstrides.hpp.

strides() [1/2]

template<class E>

auto xt::strides ( const E & e, std::size_t axis, stride_type type = stride_type::normal )

inlinenoexcept

Get stride of an object along an axis.

Parameters

a

an array

Returns

integer

Definition at line 292 of file xstrides.hpp.

strides() [2/2]

template<class E>

auto xt::strides ( const E & e, stride_type type = stride_type::normal )

inlinenoexcept

Get strides of an object.

Parameters

a

an array

Returns

array

Definition at line 248 of file xstrides.hpp.