gslice


class
<valarray> 
 class gslice;

Valarray generalized slice selector

This class represents a valarray generalized slice (multidimensional slice) selector. It does not contain any element - it only describes a selection of elements in a valarray 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 selected in each dimension.
The stride (stride) is the separation between the elements that are selected (the size of each dimension).

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:                *
                        |
size=2, stride=7:       *--------------------*
                        |                    |
size=3, stride=2:       *-----*-----*        *------*------*
                        |     |     |        |      |      |
gslice:                 *     *     *        *      *      *
                    [0][1][2][3][4][5][6][7][8][9][10][11][12][13]


Members

(constructor) gslice constructor (public member function)
gslice::start Return start of gslice (public member function)
gslice::size Return sizes of gslice (public member function)
gslice::stride Return strides of gslice (public member function)


Example

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// gslice example
#include <iostream>
#include <valarray>
using namespace std;

int main ()
{
  valarray<int> foo (14);
  for (int i=0; i<14; ++i) foo[i]=i;

  size_t start=1;
  size_t lengths[]= {2,3};
  size_t strides[]= {7,2};

  gslice mygslice (start,valarray<size_t>(lengths,2),valarray<size_t>(strides,2));

  valarray<int> bar = foo[mygslice];

  cout << "gslice: ";
  for (size_t n=0; n<bar.size(); n++)
	  cout << bar[n] << ' ';
  cout << endl;

  return 0;
}


Output

gslice: 1 3 5 8 10 12


See also

slice Valarray slice selector (class)
gslice_array Valarray gslice selection (class template)