C++ High Performance

std::for_each

Although std::for_each is mainly used for applying a functor to a range of elements, it is quite similar to std::transform() although it only processes elements, like this:

auto peruvians = std::vector<std::string>{  "Mario", "Claudio", "Sofia", "Gaston", "Alberto"}; 
std::for_each(peruvians.begin(), peruvians.end(), [](std::string& s) {
  s.resize(1); 
}); 
// Peruvians is now {"M", "C", "S", "G", "A"}  

It actually also returns the functor passed into it, which means it can be used like this:

auto result_func = std::for_each( 
  peruvians.begin(),  
  peruvians.end(),   [all_names = std::string{}](const std::string& name) mutable { 
    all_names += name + " "; 
    return all_names; 
  } 
); 
auto all_names = result_func(""); 
// all_names is now "Mario ...