std::string a container

问题

Is std::string a container class in standard c++ library, restricted to hold only char elements?

回答1:

It's a typedef of std::basic_string<char>, actually. std::basic_string is a container class specifically designed for string operations. This container can be used for wide characters (wchar_t) as well; for that case its typedef would be wstring.

回答2:

A std::basic_string<> is a class that is very much like a sequence container. Note that std::basic_string can contain any POD type, not just elements of type char (which is what a std::string is) or wchar_t (std::wstring).

I believe that a basic_string supports all the operations of a sequence container. However, note that by definition a container type can hold any assignable and copy-constructable types - not just POD types. So a basic_string is very much like a container, but strictly speaking it's not a container.

In other words there are types that can be used with a container that cannot be used with a basic_string. But for those types that can be used with a basic_string, the std::basic_string provides the full interface of a sequence container (I think) plus additional functionality.

回答3:

std::string as a typedef for basic_string<char, std::char_traits<char>, std::allocator<char> > is pretty much limited to the char type.

However, I don't think basic_string itself is necessarily limited to only character types (though, as the name suggests, it might be intended to be used for string data).

#include <string>
#include <cassert>

int main()
{
    std::basic_string<int> numbers_1, numbers_2;
    numbers_1 += 1;
    numbers_2 += 2;
    std::basic_string<int> numbers_3 = numbers_1 + numbers_2 + 3;
    unsigned pos = numbers_3.find(10);
    assert(pos == std::basic_string<int>::npos);
}

回答4:

std::string is a basic_string. It's not necessarily a char, but it has to follow the char traits http://www.cplusplus.com/reference/string/char_traits/

来源：https://stackoverflow.com/questions/1790084/stdstring-a-container