gslice_array.cpp

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#include <iostream>    // for cout, endl
#include <valarray.h>  // Includes valarray and provides stream inserter.
#include <examples.h>  // Generic header for all examples.
 
typedef std::valarray<int> valarray_t;
 
int main(void) {
 
  valarray_t::value_type
      ibuf[22] = { 0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10,
                   11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 };
 
  // Create a valarray of ints
  valarray_t  vi (ibuf,(sizeof ibuf / sizeof *ibuf));
 
  // Print out the valarray
  std::cout << "original valarray vi:\n\n" << vi << "\n\n";
 
  // Get a two dimensional diagonal slice out of the middle
  std::size_t length_ary[] = {4, 2};
  std::size_t stride_ary[] = {4, 6};
 
  std::valarray<std::size_t> length_val(length_ary, 2);
  std::valarray<std::size_t> stride_val(stride_ary, 2);
 
 
  // Print out the slices starting at positions 0 and 2 and respectively.
  std::cout << "vi[gslice(0,[4,2],[4,6])]\n\n"
            << vi[std::gslice(0,length_val,stride_val)] << "\n\n";
 
  std::cout << "vi[gslice(2,[4,2],[4,6])]\n\n"
            << vi[std::gslice(2,length_val,stride_val)] << "\n\n";
 
  // Multiply the first slice by the second.
  vi[std::gslice(0,length_val,stride_val)]
      *= static_cast<valarray_t > (vi[std::gslice(2,length_val,stride_val)]);
 
  std::cout << "vi[gslice(0,[4,2],[4,8])] *= vi[gslice(2,[4,2],[4,6])]\n\n"
            << vi << std::endl;
 
  return 0;
 
}