ceph/src/boost/libs/iterator/example/permutation_iter_example.cpp

   1 // Copyright (C) 2004 Jeremy Siek <jsiek@cs.indiana.edu>
   2 // Distributed under the Boost Software License, Version 1.0. (See
   3 // accompanying file LICENSE_1_0.txt or copy at
   4 // http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #include <iostream>
   7 #include <vector>
   8 #include <deque>
   9 #include <algorithm>
  10 #include <boost/iterator/permutation_iterator.hpp>
  11 #include <boost/cstdlib.hpp>
  12 #include <assert.h>
  13
  14
  15 int main() {
  16   using namespace boost;
  17   int i = 0;
  18
  19   typedef std::vector< int > element_range_type;
  20   typedef std::deque< int > index_type;
  21
  22   static const int element_range_size = 10;
  23   static const int index_size = 4;
  24
  25   element_range_type elements( element_range_size );
  26   for(element_range_type::iterator el_it = elements.begin() ; el_it != elements.end() ; ++el_it)
  27     *el_it = std::distance(elements.begin(), el_it);
  28
  29   index_type indices( index_size );
  30   for(index_type::iterator i_it = indices.begin() ; i_it != indices.end() ; ++i_it )
  31     *i_it = element_range_size - index_size + std::distance(indices.begin(), i_it);
  32   std::reverse( indices.begin(), indices.end() );
  33
  34   typedef permutation_iterator< element_range_type::iterator, index_type::iterator > permutation_type;
  35   permutation_type begin = make_permutation_iterator( elements.begin(), indices.begin() );
  36   permutation_type it = begin;
  37   permutation_type end = make_permutation_iterator( elements.begin(), indices.end() );
  38
  39   std::cout << "The original range is : ";
  40   std::copy( elements.begin(), elements.end(), std::ostream_iterator< int >( std::cout, " " ) );
  41   std::cout << "\n";
  42
  43   std::cout << "The reindexing scheme is : ";
  44   std::copy( indices.begin(), indices.end(), std::ostream_iterator< int >( std::cout, " " ) );
  45   std::cout << "\n";
  46
  47   std::cout << "The permutated range is : ";
  48   std::copy( begin, end, std::ostream_iterator< int >( std::cout, " " ) );
  49   std::cout << "\n";
  50
  51   std::cout << "Elements at even indices in the permutation : ";
  52   it = begin;
  53   for(i = 0; i < index_size / 2 ; ++i, it+=2 ) std::cout << *it << " ";
  54   std::cout << "\n";
  55
  56   std::cout << "Permutation backwards : ";
  57   it = begin + (index_size);
  58   assert( it != begin );
  59   for( ; it-- != begin ; ) std::cout << *it << " ";
  60   std::cout << "\n";
  61
  62   std::cout << "Iterate backward with stride 2 : ";
  63   it = begin + (index_size - 1);
  64   for(i = 0 ; i < index_size / 2 ; ++i, it-=2 ) std::cout << *it << " ";
  65   std::cout << "\n";
  66
  67   return boost::exit_success;
  68 }