std.experimental.ndslice.selection

template pack(K...)

Creates a packed slice, i.e. slice of slices. The function does not carry out any calculations, it simply returns the same binary data presented differently.

Parameters:

K	sizes of dimension packs

Returns:

pack!K returns Slice!(N-K, Slice!(K+1, Range)); slice.pack!(K1, K2, ..., Kn) is the same as slice.pack!K1.pack!K2. ... pack!Kn.

Examples:

import std.experimental.ndslice : sliced, Slice, pack;
import std.range : iota;

auto r = (3 * 4 * 5 * 6).iota;
auto a = r.sliced(3, 4, 5, 6);
auto b = a.pack!2;

static immutable res1 = [3, 4];
static immutable res2 = [5, 6];
assert(b.shape == res1);
assert(b[0, 0].shape == res2);
assert(a == b);
static assert(is(typeof(b) == typeof(a.pack!2)));
static assert(is(typeof(b) == Slice!(2, Slice!(3, typeof(r)))));

Slice!(N, Range).PureThis unpack(size_t N, Range)(Slice!(N, Range) slice);

Unpacks a packed slice.

The function does not carry out any calculations, it simply returns the same binary data presented differently.

Parameters:

Slice!(N, Range) slice

packed slice

Returns:

unpacked slice

See Also:

pack, evertPack

Examples:

auto a = iotaSlice(3, 4, 5, 6, 7, 8, 9, 10, 11);
auto b = a.pack!(2, 3).unpack();
static assert(is(typeof(a) == typeof(b)));
assert(a == b);

SliceFromSeq!(Slice!(N, Range).PureRange, NSeqEvert!(Slice!(N, Range).NSeq)) evertPack(size_t N, Range)(Slice!(N, Range) slice);

Reverses the order of dimension packs. This function is used in a functional pipeline with other selectors.

Parameters:

Slice!(N, Range) slice

packed slice

Returns:

packed slice

See Also:

pack, unpack

Examples:

import std.experimental.ndslice.iteration : transposed;
auto slice = iotaSlice(3, 4, 5, 6, 7, 8, 9, 10, 11);
assert(slice
    .pack!2
    .evertPack
    .unpack
         == slice.transposed!(
            slice.shape.length-2,
            slice.shape.length-1));

Examples:

import std.experimental.ndslice.slice;
import std.experimental.ndslice.iteration : transposed;
import std.range.primitives : ElementType;
import std.range : iota;
import std.algorithm.comparison : equal;
auto r = (3 * 4 * 5 * 6 * 7 * 8 * 9 * 10 * 11).iota;
auto a = r.sliced(3, 4, 5, 6, 7, 8, 9, 10, 11);
auto b = a
    .pack!(2, 3)
    .evertPack;
auto c = b[8, 9];
auto d = c[5, 6, 7];
auto e = d[1, 2, 3, 4];
auto g = a[1, 2, 3, 4, 5, 6, 7, 8, 9];
assert(e == g);
assert(a == b.evertPack);
assert(c == a.transposed!(7, 8, 4, 5, 6)[8, 9]);
alias R = typeof(r);
static assert(is(typeof(b) == Slice!(2, Slice!(4, Slice!(5, R)))));
static assert(is(typeof(c) == Slice!(3, Slice!(5, R))));
static assert(is(typeof(d) == Slice!(4, R)));
static assert(is(typeof(e) == ElementType!R));

Slice!(1, Range) diagonal(size_t N, Range)(Slice!(N, Range) slice);

Returns a 1-dimensional slice over the main diagonal of an n-dimensional slice. diagonal can be generalized with other selectors such as blocks (diagonal blocks) and windows (multi-diagonal slice).

Parameters:

N	dimension count
Slice!(N, Range) slice	input slice

Returns:

1-dimensional slice composed of diagonal elements

Examples:

Matrix, main diagonal

//  -------
// | 0 1 2 |
// | 3 4 5 |
//  -------
//->
// | 0 4 |
static immutable d = [0, 4];
assert(iotaSlice(2, 3).diagonal == d);

Examples:

Non-square matrix

import std.algorithm.comparison : equal;
import std.range : only;

//  -------
// | 0 1 |
// | 2 3 |
// | 4 5 |
//  -------
//->
// | 0 3 |

assert(iotaSlice(3, 2)
    .diagonal
    .equal(only(0, 3)));

Examples:

Loop through diagonal

import std.experimental.ndslice.slice;

auto slice = slice!int(3, 3);
int i;
foreach (ref e; slice.diagonal)
    e = ++i;
assert(slice == [
    [1, 0, 0],
    [0, 2, 0],
    [0, 0, 3]]);

Examples:

Matrix, subdiagonal

import std.experimental.ndslice.iteration : dropOne;
//  -------
// | 0 1 2 |
// | 3 4 5 |
//  -------
//->
// | 1 5 |
static immutable d = [1, 5];
assert(iotaSlice(2, 3).dropOne!1.diagonal == d);

Examples:

Matrix, antidiagonal

import std.experimental.ndslice.iteration : dropToHypercube, reversed;
//  -------
// | 0 1 2 |
// | 3 4 5 |
//  -------
//->
// | 1 3 |
static immutable d = [1, 3];
assert(iotaSlice(2, 3).dropToHypercube.reversed!1.diagonal == d);

Examples:

3D, main diagonal

//  -----------
// |  0   1  2 |
// |  3   4  5 |
//  - - - - - -
// |  6   7  8 |
// |  9  10 11 |
//  -----------
//->
// | 0 10 |
static immutable d = [0, 10];
assert(iotaSlice(2, 2, 3).diagonal == d);

Examples:

3D, subdiagonal

import std.experimental.ndslice.iteration : dropOne;
//  -----------
// |  0   1  2 |
// |  3   4  5 |
//  - - - - - -
// |  6   7  8 |
// |  9  10 11 |
//  -----------
//->
// | 1 11 |
static immutable d = [1, 11];
assert(iotaSlice(2, 2, 3).dropOne!2.diagonal == d);

Examples:

3D, diagonal plain

//  -----------
// |  0   1  2 |
// |  3   4  5 |
// |  6   7  8 |
//  - - - - - -
// |  9  10 11 |
// | 12  13 14 |
// | 15  16 17 |
//  - - - - - -
// | 18  20 21 |
// | 22  23 24 |
// | 24  25 26 |
//  -----------
//->
//  -----------
// |  0   4  8 |
// |  9  13 17 |
// | 18  23 26 |
//  -----------

static immutable d =
    [[ 0,  4,  8],
     [ 9, 13, 17],
     [18, 22, 26]];

auto slice = iotaSlice(3, 3, 3)
    .pack!2
    .evertPack
    .diagonal
    .evertPack;

assert(slice == d);

Slice!(N, Slice!(N + 1, Range)) blocks(size_t N, Range)(Slice!(N, Range) slice, size_t[N] lengths...);

Returns an n-dimensional slice of n-dimensional non-overlapping blocks. blocks can be generalized with other selectors. For example, blocks in combination with diagonal can be used to get a slice of diagonal blocks.

Parameters:

N	dimension count
Slice!(N, Range) slice	slice to be split into blocks
size_t[N] lengths	dimensions of block, residual blocks are ignored

Returns:

packed N-dimensional slice composed of N-dimensional slices

Examples:

import std.experimental.ndslice.slice;
auto slice = slice!int(5, 8);
auto blocks = slice.blocks(2, 3);
int i;
foreach (block; blocks.byElement)
    block[] = ++i;

assert(blocks ==
    [[[[1, 1, 1], [1, 1, 1]],
      [[2, 2, 2], [2, 2, 2]]],
     [[[3, 3, 3], [3, 3, 3]],
      [[4, 4, 4], [4, 4, 4]]]]);

assert(    slice ==
    [[1, 1, 1,  2, 2, 2,  0, 0],
     [1, 1, 1,  2, 2, 2,  0, 0],

     [3, 3, 3,  4, 4, 4,  0, 0],
     [3, 3, 3,  4, 4, 4,  0, 0],

     [0, 0, 0,  0, 0, 0,  0, 0]]);

Examples:

Diagonal blocks

import std.experimental.ndslice.slice;
auto slice = slice!int(5, 8);
auto blocks = slice.blocks(2, 3);
auto diagonalBlocks = blocks.diagonal.unpack;

diagonalBlocks[0][] = 1;
diagonalBlocks[1][] = 2;

assert(diagonalBlocks ==
    [[[1, 1, 1], [1, 1, 1]],
     [[2, 2, 2], [2, 2, 2]]]);

assert(blocks ==
    [[[[1, 1, 1], [1, 1, 1]],
      [[0, 0, 0], [0, 0, 0]]],
     [[[0, 0, 0], [0, 0, 0]],
      [[2, 2, 2], [2, 2, 2]]]]);

assert(slice ==
    [[1, 1, 1,  0, 0, 0,  0, 0],
     [1, 1, 1,  0, 0, 0,  0, 0],

     [0, 0, 0,  2, 2, 2,  0, 0],
     [0, 0, 0,  2, 2, 2,  0, 0],

     [0, 0, 0, 0, 0, 0, 0, 0]]);

Examples:

Matrix divided into vertical blocks

import std.experimental.ndslice.slice;
auto slice = slice!int(5, 13);
auto blocks = slice
    .pack!1
    .evertPack
    .blocks(3)
    .unpack
    .pack!2;

int i;
foreach (block; blocks.byElement)
    block[] = ++i;

assert(slice ==
    [[1, 1, 1,  2, 2, 2,  3, 3, 3,  4, 4, 4,  0],
     [1, 1, 1,  2, 2, 2,  3, 3, 3,  4, 4, 4,  0],
     [1, 1, 1,  2, 2, 2,  3, 3, 3,  4, 4, 4,  0],
     [1, 1, 1,  2, 2, 2,  3, 3, 3,  4, 4, 4,  0],
     [1, 1, 1,  2, 2, 2,  3, 3, 3,  4, 4, 4,  0]]);

Slice!(N, Slice!(N + 1, Range)) windows(size_t N, Range)(Slice!(N, Range) slice, size_t[N] lengths...);

Returns an n-dimensional slice of n-dimensional overlapping windows. windows can be generalized with other selectors. For example, windows in combination with diagonal can be used to get a multi-diagonal slice.

Parameters:

N	dimension count
Slice!(N, Range) slice	slice to be iterated
size_t[N] lengths	dimensions of windows

Returns:

packed N-dimensional slice composed of N-dimensional slices

Examples:

import std.experimental.ndslice.slice;
auto slice = slice!int(5, 8);
auto windows = slice.windows(2, 3);
foreach (window; windows.byElement)
    window[] += 1;

assert(slice ==
    [[1,  2,  3, 3, 3, 3,  2,  1],

     [2,  4,  6, 6, 6, 6,  4,  2],
     [2,  4,  6, 6, 6, 6,  4,  2],
     [2,  4,  6, 6, 6, 6,  4,  2],

     [1,  2,  3, 3, 3, 3,  2,  1]]);

Examples:

import std.experimental.ndslice.slice;
auto slice = slice!int(5, 8);
auto windows = slice.windows(2, 3);
windows[1, 2][] = 1;
windows[1, 2][0, 1] += 1;
windows.unpack[1, 2, 0, 1] += 1;

assert(slice ==
    [[0, 0,  0, 0, 0,  0, 0, 0],

     [0, 0,  1, 3, 1,  0, 0, 0],
     [0, 0,  1, 1, 1,  0, 0, 0],

     [0, 0,  0, 0, 0,  0, 0, 0],
     [0, 0,  0, 0, 0,  0, 0, 0]]);

Examples:

Multi-diagonal matrix

import std.experimental.ndslice.slice;
auto slice = slice!int(8, 8);
auto windows = slice.windows(3, 3);

auto multidiagonal = windows
    .diagonal
    .unpack;
foreach (window; multidiagonal)
    window[] += 1;

assert(slice ==
    [[ 1, 1, 1,  0, 0, 0, 0, 0],
     [ 1, 2, 2, 1,  0, 0, 0, 0],
     [ 1, 2, 3, 2, 1,  0, 0, 0],
     [0,  1, 2, 3, 2, 1,  0, 0],
     [0, 0,  1, 2, 3, 2, 1,  0],
     [0, 0, 0,  1, 2, 3, 2, 1],
     [0, 0, 0, 0,  1, 2, 2, 1],
     [0, 0, 0, 0, 0,  1, 1, 1]]);

Examples:

Sliding window over matrix columns

import std.experimental.ndslice.slice;
auto slice = slice!int(5, 8);
auto windows = slice
    .pack!1
    .evertPack
    .windows(3)
    .unpack
    .pack!2;


foreach (window; windows.byElement)
    window[] += 1;

assert(slice ==
    [[1,  2,  3, 3, 3, 3,  2,  1],
     [1,  2,  3, 3, 3, 3,  2,  1],
     [1,  2,  3, 3, 3, 3,  2,  1],
     [1,  2,  3, 3, 3, 3,  2,  1],
     [1,  2,  3, 3, 3, 3,  2,  1]]);

Slice!(M, Range) reshape(size_t N, Range, size_t M)(Slice!(N, Range) slice, size_t[M] lengths...);

Returns a new slice for the same data with different dimensions.

Parameters:

Slice!(N, Range) slice	slice to be reshaped
size_t[M] lengths	list of new dimensions. One of the lengths can be set to -1. In this case, the corresponding dimension is inferable.

Returns:

reshaped slice

Throws:

ReshapeException if the slice cannot be reshaped with the input lengths.

Examples:

import std.experimental.ndslice.iteration : allReversed;
auto slice = iotaSlice(3, 4)
    .allReversed
    .reshape(-1, 3);
assert(slice ==
    [[11, 10, 9],
     [ 8,  7, 6],
     [ 5,  4, 3],
     [ 2,  1, 0]]);

Examples:

Reshaping with memory allocation

import std.experimental.ndslice.slice;
import std.experimental.ndslice.iteration : reversed;
import std.array : array;

auto reshape2(S, size_t M)(S slice, size_t[M] lengths...)
{
    // Tries to reshape without allocation
    try return slice.reshape(lengths);
    catch (ReshapeException e)
        // Allocates
        return slice.slice.reshape(lengths);
}

auto slice =
    [0, 1,  2,  3,
     4, 5,  6,  7,
     8, 9, 10, 11]
    .sliced(3, 4)
    .reversed!0;

assert(reshape2(slice, 4, 3) ==
    [[ 8, 9, 10],
     [11, 4,  5],
     [ 6, 7,  0],
     [ 1, 2,  3]]);

class ReshapeException: std.experimental.ndslice.slice.SliceException;

See Also:

reshape

size_t[] lengths;

Old lengths

sizediff_t[] strides;

Old strides

size_t[] newLengths;

New lengths

pure nothrow @nogc @safe this(size_t[] lengths, sizediff_t[] strides, size_t[] newLengths, string msg, string file = __FILE__, uint line = cast(uint)904, Throwable next = null);

auto byElement(size_t N, Range)(Slice!(N, Range) slice);

Slice!(1, Range) byElement(size_t N : 1, Range)(Slice!(N, Range) slice);

Returns a random access range of all elements of a slice. The order of elements is preserved. byElement can be generalized with other selectors.

Parameters:

N	dimension count
Slice!(N, Range) slice	slice to be iterated

Returns:

random access range composed of elements of the slice

Examples:

Regular slice

import std.algorithm.comparison : equal;
import std.range : iota;
assert(iotaSlice(4, 5)
    .byElement
    .equal(20.iota));

Examples:

Packed slice

import std.experimental.ndslice.slice;
import std.experimental.ndslice.iteration;
import std.range : drop;
assert(iotaSlice(3, 4, 5, 6, 7)
    .pack!2
    .byElement()
    .drop(1)
    .front
     == iotaSlice([6, 7], 6 * 7));

Examples:

Properties

auto elems = iotaSlice(3, 4).byElement;

elems.popFrontExactly(2);
assert(elems.front == 2);
assert(elems.index == [0, 2]);

elems.popBackExactly(2);
assert(elems.back == 9);
assert(elems.length == 8);

Examples:

Index property

import std.experimental.ndslice.slice;
auto slice = new long[20].sliced(5, 4);

for (auto elems = slice.byElement; !elems.empty; elems.popFront)
{
    size_t[2] index = elems.index;
    elems.front = index[0] * 10 + index[1] * 3;
}
assert(slice ==
    [[ 0,  3,  6,  9],
     [10, 13, 16, 19],
     [20, 23, 26, 29],
     [30, 33, 36, 39],
     [40, 43, 46, 49]]);

Examples:

Random access and slicing

import std.experimental.ndslice.slice;
import std.algorithm.comparison : equal;
import std.array : array;
import std.range : iota, repeat;
static data = 20.iota.array;
auto elems = data.sliced(4, 5).byElement;

elems = elems[11 .. $ - 2];

assert(elems.length == 7);
assert(elems.front == 11);
assert(elems.back == 17);

foreach (i; 0 .. 7)
    assert(elems[i] == i + 11);

// assign an element
elems[2 .. 6] = -1;
assert(elems[2 .. 6].equal(repeat(-1, 4)));

// assign an array
static ar = [-1, -2, -3, -4];
elems[2 .. 6] = ar;
assert(elems[2 .. 6].equal(ar));

// assign a slice
ar[] *= 2;
auto sl = ar.sliced(ar.length);
elems[2 .. 6] = sl;
assert(elems[2 .. 6].equal(sl));

Examples:

Forward access works faster than random access or backward access. Use allReversed  in pipeline before byElement to achieve fast backward access.

import std.range : retro;
import std.experimental.ndslice.iteration : allReversed;

auto slice = iotaSlice(3, 4, 5);

/// Slow backward iteration #1
foreach (ref e; slice.byElement.retro)
{
    //...
}

/// Slow backward iteration #2
foreach_reverse (ref e; slice.byElement)
{
    //...
}

/// Fast backward iteration
foreach (ref e; slice.allReversed.byElement)
{
    //...
}

Examples:

byElement just return the slice for 1-dimensional case.

import std.experimental.ndslice.slice : slice;
static assert(is(typeof(slice!int(100)) == Slice!(1, int*)));

auto byElementInStandardSimplex(size_t N, Range)(Slice!(N, Range) slice, size_t maxHypercubeLength = size_t.max);

Slice!(1, Range) byElementInStandardSimplex(size_t N : 1, Range)(Slice!(N, Range) slice, size_t maxHypercubeLength = size_t.max);

Returns an forward range of all elements of standard simplex of a slice. In case the slice has two dimensions, it is composed of elements of upper left triangular matrix. The order of elements is preserved. byElementInStandardSimplex can be generalized with other selectors.

Parameters:

N	dimension count
Slice!(N, Range) slice	slice to be iterated
size_t maxHypercubeLength	maximal length of simplex hypercube.

Returns:

forward range composed of all elements of standard simplex of the slice

Examples:

import std.experimental.ndslice.slice;
auto slice = slice!int(4, 5);
auto elems = slice
    .byElementInStandardSimplex;
int i;
foreach (ref e; elems)
    e = ++i;
assert(slice ==
    [[ 1, 2, 3, 4, 0],
     [ 5, 6, 7, 0, 0],
     [ 8, 9, 0, 0, 0],
     [10, 0, 0, 0, 0]]);

Examples:

import std.experimental.ndslice.slice;
import std.experimental.ndslice.iteration;
auto slice = slice!int(4, 5);
auto elems = slice
    .transposed
    .allReversed
    .byElementInStandardSimplex;
int i;
foreach (ref e; elems)
    e = ++i;
assert(slice ==
    [[0,  0, 0, 0, 4],
     [0,  0, 0, 7, 3],
     [0,  0, 9, 6, 2],
     [0, 10, 8, 5, 1]]);

Examples:

Properties

import std.range.primitives : popFrontN;

auto elems = iotaSlice(3, 4).byElementInStandardSimplex;

elems.popFront;
assert(elems.front == 1);
assert(elems.index == cast(size_t[2])[0, 1]);

elems.popFrontN(3);
assert(elems.front == 5);

Examples:

Save

auto elems = iotaSlice(3, 4).byElementInStandardSimplex;
import std.range : dropOne, popFrontN;
elems.popFrontN(4);

assert(elems.save.dropOne.front == 8);
assert(elems.front == 5);
assert(elems.index == cast(size_t[2])[1, 1]);
assert(elems.length == 2);

Examples:

byElementInStandardSimplex returns a corresponding part of the slice for 1-dimensional case.

auto sl = iotaSlice(7);
auto simplex = sl.byElementInStandardSimplex;

assert(simplex == [0, 1, 2, 3, 4, 5, 6]);

static assert(is(typeof(simplex) == typeof(sl)));

assert(sl.byElementInStandardSimplex(3) == [0, 1, 2]);

IndexSlice!N indexSlice(size_t N)(size_t[N] lengths...);

Returns a slice, the elements of which are equal to the initial multidimensional index value. This is multidimensional analog of std.range.iota. For a flattened (continuous) index, see iotaSlice.

Parameters:

N	dimension count
size_t[N] lengths	list of dimension lengths

Returns:

N-dimensional slice composed of indexes

See Also:

IndexSlice, iotaSlice

Examples:

auto slice = indexSlice(2, 3);
static immutable array =
    [[[0, 0], [0, 1], [0, 2]],
     [[1, 0], [1, 1], [1, 2]]];

assert(slice == array);


static assert(is(IndexSlice!2 : Slice!(2, Range), Range));
static assert(is(DeepElementType!(IndexSlice!2) == size_t[2]));

Examples:

auto im = indexSlice(7, 9);

assert(im[2, 1] == [2, 1]);

//slicing works correctly
auto cm = im[1 .. $, 4 .. $];
assert(cm[2, 1] == [3, 5]);

template IndexSlice(size_t N) if (N)

Slice composed of indexes.

See Also:

indexSlice

IotaSlice!N iotaSlice(size_t N)(size_t[N] lengths...);

IotaSlice!N iotaSlice(size_t N)(size_t[N] lengths, size_t shift);

IotaSlice!N iotaSlice(size_t N)(size_t[N] lengths, size_t shift, size_t step);

Returns a slice, the elements of which are equal to the initial flattened index value. For a multidimensional index, see indexSlice.

Parameters:

N	dimension count
size_t[N] lengths	list of dimension lengths
size_t shift	value of the first element in a slice (optional)
size_t step	value of the step between elements (optional)

Returns:

N-dimensional slice composed of indexes

See Also:

IotaSlice, indexSlice

Examples:

auto slice = iotaSlice(2, 3);
static immutable array =
    [[0, 1, 2],
     [3, 4, 5]];

assert(slice == array);

import std.range.primitives : isRandomAccessRange;
static assert(isRandomAccessRange!(IotaSlice!2));
static assert(is(IotaSlice!2 : Slice!(2, Range), Range));
static assert(is(DeepElementType!(IotaSlice!2) == size_t));

Examples:

auto im = iotaSlice([10, 5], 100);

assert(im[2, 1] == 111); // 100 + 2 * 5 + 1

//slicing works correctly
auto cm = im[1 .. $, 3 .. $];
assert(cm[2, 1] == 119); // 119 = 100 + (1 + 2) * 5 + (3 + 1)

Examples:

iotaSlice with step

auto sl = iotaSlice([2, 3], 10, 10);

assert(sl == [[10, 20, 30],
              [40, 50, 60]]);

template IotaSlice(size_t N) if (N)

Slice composed of flattened indexes.

See Also:

iotaSlice

RepeatSlice!(M, T) repeatSlice(T, size_t M)(T value, size_t[M] lengths...)
if (!is(T : Slice!(N, Range), size_t N, Range));

Slice!(M, Slice!(N + 1, Range)) repeatSlice(size_t N, Range, size_t M)(Slice!(N, Range) slice, size_t[M] lengths...);

Returns a slice with identical elements. RepeatSlice stores only single value.

Parameters:

size_t[M] lengths

list of dimension lengths

Returns:

n-dimensional slice composed of identical values, where n is dimension count.

See Also:

std.range.repeat

Examples:

auto sl = iotaSlice(3)
    .repeatSlice(4);
assert(sl == [[0, 1, 2],
              [0, 1, 2],
              [0, 1, 2],
              [0, 1, 2]]);

Examples:

import std.experimental.ndslice.iteration : transposed;

auto sl = iotaSlice(3)
    .repeatSlice(4)
    .unpack
    .transposed;

assert(sl == [[0, 0, 0, 0],
              [1, 1, 1, 1],
              [2, 2, 2, 2]]);

Examples:

import std.experimental.ndslice.slice : slice;

auto sl = iotaSlice([3], 6).slice;
auto slC = sl.repeatSlice(2, 3);
sl[1] = 4;
assert(slC == [[[6, 4, 8],
                [6, 4, 8],
                [6, 4, 8]],
               [[6, 4, 8],
                [6, 4, 8],
                [6, 4, 8]]]);

Examples:

auto sl = repeatSlice(4.0, 2, 3);
assert(sl == [[4.0, 4.0, 4.0],
              [4.0, 4.0, 4.0]]);

static assert(is(DeepElementType!(typeof(sl)) == double));

sl[1, 1] = 3;
assert(sl == [[3.0, 3.0, 3.0],
              [3.0, 3.0, 3.0]]);

template RepeatSlice(size_t N, T) if (N)

Slice composed of identical values.

template mapSlice(fun...) if (fun.length)

Implements the homonym function (also known as transform) present in many languages of functional flavor. The call mapSlice!(fun)(tensor) returns a tensor of which elements are obtained by applying fun for all elements in tensor. The original tensors are not changed. Evaluation is done lazily.

Note: transposed  and pack  can be used to specify dimensions.

Parameters:

fun	One or more functions.
Slice!(N, Range) tensor	An input tensor.

Returns:

a tensor with each fun applied to all the elements. If there is more than one fun, the element type will be Tuple containing one element for each fun.

See Also:

std.algorithm.iteration.map Map (higher-order function)

Examples:

import std.experimental.ndslice.selection : iotaSlice;

auto s = iotaSlice(2, 3).mapSlice!(a => a * 3);
assert(s == [[ 0,  3,  6],
             [ 9, 12, 15]]);

Examples:

Packed tensors.

import std.experimental.ndslice.selection : iotaSlice, windows;

//  iotaSlice        windows     mapSlice  sums ( ndFold!"a + b" )
//                --------------
//  -------      |  ---    ---  |      ------
// | 0 1 2 |  => || 0 1 || 1 2 ||  => | 8 12 |
// | 3 4 5 |     || 3 4 || 4 5 ||      ------
//  -------      |  ---    ---  |
//                --------------
auto s = iotaSlice(2, 3)
    .windows(2, 2)
    .mapSlice!((a) {
        size_t s;
        foreach (r; a)
            foreach (e; r)
                s += e;
        return s;
        });

assert(s == [[8, 12]]);

Examples:

Zipped tensors

import std.experimental.ndslice.slice : assumeSameStructure;
import std.experimental.ndslice.selection : iotaSlice;

// 0 1 2
// 3 4 5
auto sl1 = iotaSlice(2, 3);
// 1 2 3
// 4 5 6
auto sl2 = iotaSlice([2, 3], 1);

// tensors must have the same strides
assert(sl1.structure == sl2.structure);

auto zip = assumeSameStructure!("a", "b")(sl1, sl2);

auto lazySum = zip.mapSlice!(z => z.a + z.b);

assert(lazySum == [[ 1,  3,  5],
                   [ 7,  9, 11]]);

Examples:

Multiple functions can be passed to mapSlice. In that case, the element type of mapSlice is a tuple containing one element for each function.

import std.experimental.ndslice.selection : iotaSlice;

auto s = iotaSlice(2, 3).mapSlice!("a + a", "a * a");

auto sums     = [[0, 2, 4], [6,  8, 10]];
auto products = [[0, 1, 4], [9, 16, 25]];

foreach (i; 0..s.length!0)
foreach (j; 0..s.length!1)
{
    auto values = s[i, j];
    assert(values[0] == sums[i][j]);
    assert(values[1] == products[i][j]);
}

Examples:

You may alias mapSlice with some function(s) to a symbol and use it separately:

import std.conv : to;
import std.experimental.ndslice.selection : iotaSlice;

alias stringize = mapSlice!(to!string);
assert(stringize(iotaSlice(2, 3)) == [["0", "1", "2"], ["3", "4", "5"]]);

auto mapSlice(size_t N, Range)(Slice!(N, Range) tensor);