ceph/src/boost/libs/iterator/doc/indirect_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 prints an array of characters, using
   9 ``indirect_iterator`` to access the array of characters through an
  10 array of pointers. Next ``indirect_iterator`` is used with the
  11 ``transform`` algorithm to copy the characters (incremented by one) to
  12 another array. A constant indirect iterator is used for the source and
  13 a mutable indirect iterator is used for the destination. The last part
  14 of the example prints the original array of characters, but this time
  15 using the ``make_indirect_iterator`` helper function.
  16
  17
  18 ::
  19
  20     char characters[] = "abcdefg";
  21     const int N = sizeof(characters)/sizeof(char) - 1; // -1 since characters has a null char
  22     char* pointers_to_chars[N];                        // at the end.
  23     for (int i = 0; i < N; ++i)
  24       pointers_to_chars[i] = &characters[i];
  25
  26     // Example of using indirect_iterator
  27
  28     boost::indirect_iterator<char**, char>
  29       indirect_first(pointers_to_chars), indirect_last(pointers_to_chars + N);
  30
  31     std::copy(indirect_first, indirect_last, std::ostream_iterator<char>(std::cout, ","));
  32     std::cout << std::endl;
  33
  34
  35     // Example of making mutable and constant indirect iterators
  36
  37     char mutable_characters[N];
  38     char* pointers_to_mutable_chars[N];
  39     for (int j = 0; j < N; ++j)
  40       pointers_to_mutable_chars[j] = &mutable_characters[j];
  41
  42     boost::indirect_iterator<char* const*> mutable_indirect_first(pointers_to_mutable_chars),
  43       mutable_indirect_last(pointers_to_mutable_chars + N);
  44     boost::indirect_iterator<char* const*, char const> const_indirect_first(pointers_to_chars),
  45       const_indirect_last(pointers_to_chars + N);
  46
  47     std::transform(const_indirect_first, const_indirect_last,
  48                    mutable_indirect_first, std::bind1st(std::plus<char>(), 1));
  49
  50     std::copy(mutable_indirect_first, mutable_indirect_last,
  51               std::ostream_iterator<char>(std::cout, ","));
  52     std::cout << std::endl;
  53
  54
  55     // Example of using make_indirect_iterator()
  56
  57     std::copy(boost::make_indirect_iterator(pointers_to_chars),
  58               boost::make_indirect_iterator(pointers_to_chars + N),
  59               std::ostream_iterator<char>(std::cout, ","));
  60     std::cout << std::endl;
  61
  62
  63 The output is::
  64
  65     a,b,c,d,e,f,g,
  66     b,c,d,e,f,g,h,
  67     a,b,c,d,e,f,g,
  68
  69
  70 The source code for this example can be found `here`__.
  71
  72 __ ../example/indirect_iterator_example.cpp
  73