Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

filtered

filtered

filtered example

Syntax	Code
Pipe	`rng \| boost::adaptors::filtered(pred)`
Function	`boost::adaptors::filter(rng, pred)`

Precondition: The value_type of the range is convertible to the argument type of pred.
Postcondition: For all adjacent elements [x] in the returned range, pred(x) is true.
Throws: Whatever the copy constructor of pred might throw.
Range Category: Forward Range
Range Return Type: boost::filtered_range<decltype(rng)>
Returned Range Category: The minimum of the range category of rng and Bidirectional Range

filtered example

#include <boost/range/adaptor/filtered.hpp>
#include <boost/range/algorithm/copy.hpp>
#include <boost/assign.hpp>
#include <iterator>
#include <iostream>
#include <vector>

struct is_even
{
    bool operator()( int x ) const { return x % 2 == 0; }
};

int main(int argc, const char* argv[])
{
    using namespace boost::assign;
    using namespace boost::adaptors;

    std::vector<int> input;
    input += 1,2,3,4,5,6,7,8,9;

    boost::copy(
        input | filtered(is_even()),
        std::ostream_iterator<int>(std::cout, ","));

    return 0;
}

This would produce the output:

2,4,6,8,