| .. Copyright David Abrahams 2006. Distributed under the Boost |
| .. Software License, Version 1.0. (See accompanying |
| .. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
| |
| :: |
| |
| using namespace boost; |
| int i = 0; |
| |
| typedef std::vector< int > element_range_type; |
| typedef std::list< int > index_type; |
| |
| static const int element_range_size = 10; |
| static const int index_size = 4; |
| |
| element_range_type elements( element_range_size ); |
| for(element_range_type::iterator el_it = elements.begin() ; el_it != elements.end() ; ++el_it) |
| *el_it = std::distance(elements.begin(), el_it); |
| |
| index_type indices( index_size ); |
| for(index_type::iterator i_it = indices.begin() ; i_it != indices.end() ; ++i_it ) |
| *i_it = element_range_size - index_size + std::distance(indices.begin(), i_it); |
| std::reverse( indices.begin(), indices.end() ); |
| |
| typedef permutation_iterator< element_range_type::iterator, index_type::iterator > permutation_type; |
| permutation_type begin = make_permutation_iterator( elements.begin(), indices.begin() ); |
| permutation_type it = begin; |
| permutation_type end = make_permutation_iterator( elements.begin(), indices.end() ); |
| |
| std::cout << "The original range is : "; |
| std::copy( elements.begin(), elements.end(), std::ostream_iterator< int >( std::cout, " " ) ); |
| std::cout << "\n"; |
| |
| std::cout << "The reindexing scheme is : "; |
| std::copy( indices.begin(), indices.end(), std::ostream_iterator< int >( std::cout, " " ) ); |
| std::cout << "\n"; |
| |
| std::cout << "The permutated range is : "; |
| std::copy( begin, end, std::ostream_iterator< int >( std::cout, " " ) ); |
| std::cout << "\n"; |
| |
| std::cout << "Elements at even indices in the permutation : "; |
| it = begin; |
| for(i = 0; i < index_size / 2 ; ++i, it+=2 ) std::cout << *it << " "; |
| std::cout << "\n"; |
| |
| std::cout << "Permutation backwards : "; |
| it = begin + (index_size); |
| assert( it != begin ); |
| for( ; it-- != begin ; ) std::cout << *it << " "; |
| std::cout << "\n"; |
| |
| std::cout << "Iterate backward with stride 2 : "; |
| it = begin + (index_size - 1); |
| for(i = 0 ; i < index_size / 2 ; ++i, it-=2 ) std::cout << *it << " "; |
| std::cout << "\n"; |
| |
| |
| The output is:: |
| |
| The original range is : 0 1 2 3 4 5 6 7 8 9 |
| The reindexing scheme is : 9 8 7 6 |
| The permutated range is : 9 8 7 6 |
| Elements at even indices in the permutation : 9 7 |
| Permutation backwards : 6 7 8 9 |
| Iterate backward with stride 2 : 6 8 |
| |
| |
| The source code for this example can be found `here`__. |
| |
| __ ../example/permutation_iter_example.cpp |