Boost C++ Libraries

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indexed

indexed

indexed example

Syntax	Code
Pipe	`rng \| boost::adaptors::indexed`
Function	`boost::adaptors::index(rng)`

Returns: A range adapted to return both the element and the associated index. The returned range consists of iterators that have in addition to the usual iterator member functions an index() member function that returns the appropriate index for the element in the sequence corresponding with the iterator.
Range Category: Single Pass Range
Range Return Type: boost::indexed_range<typeof(rng)>
Returned Range Category: The range category of rng

indexed example

#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