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Pipe |
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Function |
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value_type
of the range is an instantiation
of std::pair
.
x
in the returned
range, x
is the result
of y.first
where y
is the corresponding element in the original range.
boost::select_first_range<typeof(rng)>
rng
.
#include <boost/range/adaptor/map.hpp> #include <boost/range/algorithm/copy.hpp> #include <boost/assign.hpp> #include <iterator> #include <iostream> #include <map> #include <vector> int main(int argc, const char* argv[]) { using namespace boost::assign; using namespace boost::adaptors; std::map<int,int> input; for (int i = 0; i < 10; ++i) input.insert(std::make_pair(i, i * 10)); boost::copy( input | map_keys, std::ostream_iterator<int>(std::cout, ",")); return 0; }
This would produce the output:
0,1,2,3,4,5,6,7,8,9,