How can I avoid “for” loops with an “if” condition inside them with C++?

Question

With almost all code I write, I am often dealing with set reduction problems on collections that ultimately end up with naive \"if\" conditions inside of them. Here\'s a simple

Answer 1

Boost provides ranges that can be used w/ range-based for. Ranges have the advantage that they don't copy the underlying data structure, they merely provide a 'view' (that is, begin(), end() for the range and operator++(), operator==() for the iterator). This might be of your interest: http://www.boost.org/libs/range/doc/html/range/reference/adaptors/reference/filtered.html

#include 
#include 
#include 

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

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

    std::vector myCollection{1,2,3,4,5,6,7,8,9};

    for( int i: myCollection | filtered( is_even() ) )
    {
        std::cout << i;
    }
}