How do I get a const_iterator using auto?
First question: is it possible to "force" a const_iterator using auto?
For example:
map<int> usa;
//...init usa
auto city_it = usa.find("New York");
I just want to query, instead of changing anything pointed by city_it, so I'd like to have city_it to be map<int>::const_iterator. But by using auto, city_it is the same to the return type of map::find(), which is map<int>::iterator. Any suggestion?
Answer
Sorry, but I just think the best suggestion is not using auto at all, since you want to perform a (implicitly valid) type conversion. auto is meant for deducing the exact type, which is not what you want here.
Just write it this way:
std::map<std::string, int>::const_iterator city_it = usa.find("New York");
As correctly pointed out by MooingDuck, using type aliases can improve the readability and maintainability of your code:
typedef std::map<std::string, int> my_map;
my_map::const_iterator city_it = usa.find("New York");