An example of the Escalator project at work.

demo.cpp

std::vector<int> a = { 3, 1, 4, 4, 2 };
std::vector<int> res6 = lift(a)
    .zipWithIndex()
    .filter( []( const std::pair<int, size_t>& v ) { return v.second > 0; } )
    .map( []( const std::pair<int, size_t>& v ) { return v.first; } )
    .toVec();
BOOST_CHECK_EQUAL( res6.size(), 4 );
CHECK_SAME_ELEMENTS( res6, std::vector<int> { 1, 4, 4, 2 } );