How do I get a const_iterator using auto?

Question

First question: is it possible to \"force\" a const_iterator using auto? For example:

map usa         


        

Answer 1

This isn't a drastically different take on conversion to const in comparision to @Jollymorphic's answer, but I think that having a utility one-liner function like this is handy:

template<class T> T const& constant(T& v){ return v; }

Which makes the conversion much more appealing to the eye:

auto it = constant(usa).find("New York");
// other solutions for direct lengths comparision
std::map<std::string, int>::const_iterator city_it = usa.find("New York");
auto city_it = const_cast<const std::map<std::string, int>&>(usa).find("New York");

Well, I'd say, bigger isn't always better. You can of course choose the name of the function according to your preferences - as_const or just const_ are possible alternatives.

Answer 2

In C++11, you can do this:

decltype(usa)::const_iterator city_it = usa.find("New York");