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:
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start=1: *
|
size=2, stride=7: *--------------------*
| |
size=3, stride=2: *-----*-----* *------*------*
| | | | | |
gslice: * * * * * *
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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;
}
Output
See also
- slice
- Valarray slice selector (class)
- gslice_array
- Valarray gslice selection (class template)