Does std::map::iterator return a copy of value or a value itself?

Question

I\'m trying to create a map inside a map:

typedef map inner_map;
typedef map outer_map;

Will I be ab

Answer 1

I want to add a follow up answer to this question for people using C++11 iterators...

The following code:

std::map m({{"a","b"},{"c","d"}});
for (auto i : m)
{
    std::cout << i.first << ": " << i.second << std::endl;
}

does copy the key and value since "auto" is a value by default, not a const reference (at least that's how it behaves clang 3.1).

Additionally, the code:

std::map m({{"a","b"},{"c","d"}});
for (const std::pair& i : m)
{
    std::cout << i.first << ": " << i.second << std::endl;
}

also copies the key and value since the correct code should be:

std::map m({{"a","b"},{"c","d"}});
for (const auto& i : m)
{
    std::cout << i.first << ": " << i.second << std::endl;
}

or

std::map m({{"a","b"},{"c","d"}});
for (const std::pair& i : m)
{
    std::cout << i.first << ": " << i.second << std::endl;
}