libs/range/doc/reference/adaptors/map_values.qbk

[/
    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:map_values map_values]

[table
    [[Syntax] [Code]]
    [[Pipe] [`rng | boost::adaptors::map_values`]]
    [[Function] [`boost::adaptors::values(rng)`]]
]

* [*Precondition:] The `value_type` of the range is an instantiation of `std::pair`.
* [*Postcondition:] For all elements `x` in the returned range, `x` is the result of `y.second` where `y` is the corresponding element in the original range.
* [*Range Category:] __single_pass_range__
* [*Range Return Type:] for constant ranges, `boost::select_second_const<typeof(rng)>` otherwise `boost:select_second_mutable<typeof(rng)>`
* [*Returned Range Category:] The range category of `rng`.

[section:map_values_example map_values example]
``
#include <boost/range/adaptor/map.hpp>
#include <boost/range/algorithm/copy.hpp>
#include <boost/assign.hpp>
#include <algorithm>
#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_values,
        std::ostream_iterator<int>(std::cout, ","));

    return 0;
}
``
[endsect]

This would produce the output:
``
0,10,20,30,40,50,60,70,80,90
``
[endsect]