forked from boostorg/range
48 lines
1.1 KiB
Plaintext
48 lines
1.1 KiB
Plaintext
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[section:map_keys map_keys]
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[table
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[[Syntax] [Code]]
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[[Pipe] [`rng | boost::adaptors::map_keys`]]
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[[Function] [`boost::adaptors::keys(rng)`]]
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]
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* [*Precondition:] The `value_type` of the range is an instantiation of `std::pair`.
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* [*Postcondition:] For all elements `x` in the returned range, `x` is the result of `y.first` where `y` is the corresponding element in the original range.
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* [*Range Category:] `SinglePassRange`
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[section:map_keys_example map_keys example]
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``
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#include <boost/range/adaptor/map.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 <map>
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#include <vector>
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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::map<int,int> input;
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for (int i = 0; i < 10; ++i)
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input.insert(std::make_pair(i, i * 10));
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boost::copy(
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input | map_keys,
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std::ostream_iterator<int>(std::cout, ","));
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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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0,1,2,3,4,5,6,7,8,9
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``
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[endsect]
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