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index()
member function that returns the appropriate index for the element
in the sequence corresponding with the iterator.
boost::indexed_range<typeof(rng)>
rng
#include <boost/range/adaptor/indexed.hpp> #include <boost/range/algorithm/copy.hpp> #include <boost/assign.hpp> #include <algorithm> #include <iostream> #include <vector> template<class Iterator> void display_element_and_index(Iterator first, Iterator last) { for (Iterator it = first; it != last; ++it) { std::cout << "Element = " << *it << " Index = " << it.index() << std::endl; } } template<class SinglePassRange> void display_element_and_index(const SinglePassRange& rng) { display_element_and_index(boost::begin(rng), boost::end(rng)); } template<class Iterator1, class Iterator2> void check_element_and_index( Iterator1 test_first, Iterator1 test_last, Iterator2 reference_first, Iterator2 reference_last) { BOOST_CHECK_EQUAL( std::distance(test_first, test_last), std::distance(reference_first, reference_last) ); int reference_index = 0; Iterator1 test_it = test_first; Iterator2 reference_it = reference_first; for (; test_it != test_last; ++test_it, ++reference_it, ++reference_index) { BOOST_CHECK_EQUAL( *test_it, *reference_it ); BOOST_CHECK_EQUAL( test_it.index(), reference_index ); } } int main(int argc, const char* argv[]) { using namespace boost::assign; using namespace boost::adaptors; std::vector<int> input; input += 10,20,30,40,50,60,70,80,90; display_element_and_index( input | indexed(0) ); return 0; }
This would produce the output:
Element = 10 Index = 0 Element = 20 Index = 1 Element = 30 Index = 2 Element = 40 Index = 3 Element = 50 Index = 4 Element = 60 Index = 5 Element = 70 Index = 6 Element = 80 Index = 7 Element = 90 Index = 8