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[/
Copyright 2010 Neil Groves
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)
/]
[section:indexed indexed]
[table
[[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`
[section:indexed_example 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;
}
``
[endsect]
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
``
[endsect]
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