ceph/src/boost/libs/iterator/doc/transform_iterator_eg.rst

   1 .. Copyright David Abrahams 2006. Distributed under the Boost
   2 .. Software License, Version 1.0. (See accompanying
   3 .. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   4
   5 Example
   6 .......
   7
   8 This is a simple example of using the transform_iterators class to
   9 generate iterators that multiply (or add to) the value returned by
  10 dereferencing the iterator. It would be cooler to use lambda library
  11 in this example.
  12
  13 ::
  14
  15     int x[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
  16     const int N = sizeof(x)/sizeof(int);
  17
  18     typedef boost::binder1st< std::multiplies<int> > Function;
  19     typedef boost::transform_iterator<Function, int*> doubling_iterator;
  20
  21     doubling_iterator i(x, boost::bind1st(std::multiplies<int>(), 2)),
  22       i_end(x + N, boost::bind1st(std::multiplies<int>(), 2));
  23
  24     std::cout << "multiplying the array by 2:" << std::endl;
  25     while (i != i_end)
  26       std::cout << *i++ << " ";
  27     std::cout << std::endl;
  28
  29     std::cout << "adding 4 to each element in the array:" << std::endl;
  30     std::copy(boost::make_transform_iterator(x, boost::bind1st(std::plus<int>(), 4)),
  31               boost::make_transform_iterator(x + N, boost::bind1st(std::plus<int>(), 4)),
  32               std::ostream_iterator<int>(std::cout, " "));
  33     std::cout << std::endl;
  34
  35
  36 The output is::
  37
  38     multiplying the array by 2:
  39     2 4 6 8 10 12 14 16
  40     adding 4 to each element in the array:
  41     5 6 7 8 9 10 11 12
  42
  43
  44 The source code for this example can be found `here`__.
  45
  46 __ ../example/transform_iterator_example.cpp