How do we print out the value_type of a C++ STL container?

Question

I know that STL containers have a value_type parameter and I've seen how it can be used to declare a type of a variable like:

vector<int>::value_type foo;

But can we just print this value_type to a console?

I want to see "string" in this example:

int main() {
    vector<string> v = {"apple", "facebook", "microsoft", "google"};
    cout << v << endl;
    cout << v.value_type << endl;
    return 0;
}

Answer 1

X::value_type is no different from any other type alias (aka typedef) in this regard — C++ has no native way of converting a type to its source code string representation (not the least because that could be ambiguous). What you can do is use std::type_info::name:

cout << typeid(decltype(v)::value_type).name() << endl;

The resulting text is compiler dependent (and not even guaranteed to be easily human readable). It will be consistent within the same build of a program, but you cannot expect it to be the same across different compilers. In other words, it's useful for debugging, but cannot reliably be used in a persistent fashion.