class
<valarray>
std::gslice
Valarray generalized slice selector
This class represents a valarray generalized slice selector (a multidimensional slice). It does not contain nor refers to any element - it only describes a selection of elements to be used as an index in valarray::operator[].
A valarray generalized slice is specified by a starting index, a set of sizes, and a set of strides. It produces a multidimensional combination of slice selections, where:
The starting index (start) is the index of the first element in the selection.
The size (size) is the number of elements in the selection.
The stride (stride) is the span that separates the elements selected.
For example, a gslice with:
start = 1
size = {2, 3}
stride = {7, 2}
would select:
[0][1][2][3][4][5][6][7][8][9][10][11][12][13]
start=1: *
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size=2, stride=7: *--------------------*
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size=3, stride=2: *-----*-----* *------*------*
| | | | | |
gslice: * * * * * *
[0][1][2][3][4][5][6][7][8][9][10][11][12][13]
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Example
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// gslice example
#include <iostream> // std::cout
#include <cstddef> // std::size_t
#include <valarray> // std::valarray, std::gslice
int main ()
{
std::valarray<int> foo (14);
for (int i=0; i<14; ++i) foo[i]=i;
std::size_t start=1;
std::size_t lengths[]= {2,3};
std::size_t strides[]= {7,2};
std::gslice mygslice (start,
std::valarray<std::size_t>(lengths,2),
std::valarray<std::size_t>(strides,2));
std::valarray<int> bar = foo[mygslice];
std::cout << "gslice:";
for (std::size_t n=0; n<bar.size(); n++)
std::cout << ' ' << bar[n];
std::cout << '\n';
return 0;
}
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Output
See also
- slice
- Valarray slice selector (class)
- gslice_array
- Valarray gslice selection (class template)