forked from boostorg/range
94 lines
2.6 KiB
Plaintext
94 lines
2.6 KiB
Plaintext
[/
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Copyright 2010 Neil Groves
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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/]
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[section:indexed indexed]
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[table
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[[Syntax] [Code]]
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[[Pipe] [`rng | boost::adaptors::indexed`]]
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[[Function] [`boost::adaptors::index(rng)`]]
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]
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* [*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.
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* [*Range Category:] __single_pass_range__
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* [*Range Return Type:] `boost::indexed_range<typeof(rng)>`
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* [*Returned Range Category:] The range category of `rng`
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[section:indexed_example indexed example]
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``
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#include <boost/range/adaptor/indexed.hpp>
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#include <boost/range/algorithm/copy.hpp>
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#include <boost/assign.hpp>
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#include <algorithm>
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#include <iostream>
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#include <vector>
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template<class Iterator>
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void display_element_and_index(Iterator first, Iterator last)
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{
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for (Iterator it = first; it != last; ++it)
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{
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std::cout << "Element = " << *it << " Index = " << it.index() << std::endl;
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}
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}
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template<class SinglePassRange>
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void display_element_and_index(const SinglePassRange& rng)
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{
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display_element_and_index(boost::begin(rng), boost::end(rng));
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}
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template<class Iterator1, class Iterator2>
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void check_element_and_index(
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Iterator1 test_first,
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Iterator1 test_last,
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Iterator2 reference_first,
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Iterator2 reference_last)
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{
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BOOST_CHECK_EQUAL( std::distance(test_first, test_last),
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std::distance(reference_first, reference_last) );
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int reference_index = 0;
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Iterator1 test_it = test_first;
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Iterator2 reference_it = reference_first;
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for (; test_it != test_last; ++test_it, ++reference_it, ++reference_index)
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{
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BOOST_CHECK_EQUAL( *test_it, *reference_it );
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BOOST_CHECK_EQUAL( test_it.index(), reference_index );
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}
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}
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int main(int argc, const char* argv[])
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{
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using namespace boost::assign;
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using namespace boost::adaptors;
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std::vector<int> input;
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input += 10,20,30,40,50,60,70,80,90;
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display_element_and_index( input | indexed(0) );
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return 0;
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}
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``
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[endsect]
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This would produce the output:
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``
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Element = 10 Index = 0
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Element = 20 Index = 1
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Element = 30 Index = 2
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Element = 40 Index = 3
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Element = 50 Index = 4
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Element = 60 Index = 5
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Element = 70 Index = 6
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Element = 80 Index = 7
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Element = 90 Index = 8
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``
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[endsect]
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