ceph/src/boost/libs/iterator/doc/filter_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 example uses ``filter_iterator`` and then
   9 ``make_filter_iterator`` to output only the positive integers from an
  10 array of integers. Then ``make_filter_iterator`` is is used to output
  11 the integers greater than ``-2``.
  12
  13 ::
  14
  15     struct is_positive_number {
  16       bool operator()(int x) { return 0 < x; }
  17     };
  18
  19     int main()
  20     {
  21       int numbers_[] = { 0, -1, 4, -3, 5, 8, -2 };
  22       const int N = sizeof(numbers_)/sizeof(int);
  23
  24       typedef int* base_iterator;
  25       base_iterator numbers(numbers_);
  26
  27       // Example using filter_iterator
  28       typedef boost::filter_iterator<is_positive_number, base_iterator>
  29         FilterIter;
  30
  31       is_positive_number predicate;
  32       FilterIter filter_iter_first(predicate, numbers, numbers + N);
  33       FilterIter filter_iter_last(predicate, numbers + N, numbers + N);
  34
  35       std::copy(filter_iter_first, filter_iter_last, std::ostream_iterator<int>(std::cout, " "));
  36       std::cout << std::endl;
  37
  38       // Example using make_filter_iterator()
  39       std::copy(boost::make_filter_iterator<is_positive_number>(numbers, numbers + N),
  40                 boost::make_filter_iterator<is_positive_number>(numbers + N, numbers + N),
  41                 std::ostream_iterator<int>(std::cout, " "));
  42       std::cout << std::endl;
  43
  44       // Another example using make_filter_iterator()
  45       std::copy(
  46           boost::make_filter_iterator(
  47               std::bind2nd(std::greater<int>(), -2)
  48             , numbers, numbers + N)
  49
  50         , boost::make_filter_iterator(
  51               std::bind2nd(std::greater<int>(), -2)
  52             , numbers + N, numbers + N)
  53
  54         , std::ostream_iterator<int>(std::cout, " ")
  55       );
  56
  57       std::cout << std::endl;
  58
  59       return boost::exit_success;
  60     }
  61
  62
  63 The output is::
  64
  65     4 5 8
  66     4 5 8
  67     0 -1 4 5 8
  68
  69
  70 The source code for this example can be found `here`__.
  71
  72 __ ../example/filter_iterator_example.cpp