Declaring strings as std:string in C++

Question

This is based on GCC/G++ and usually on Ubuntu.

Here\'s my sample program I\'ve done:

#include 

using namespace std;

int main()
{
          


        

Answer 1

First problem:

First of all, you are missing the #include directive. You cannot rely on other headers (such as ) to #include the header automatically. Apart from this:

Second problem:

Writing the string declaration as std:string also works fine. What's the difference.

That is because you have an (evil) using directive at global namespace scope:

using namespace std;

The effect of this directive is that all names from the std namespace are imported into the global namespace. This is why the fully-qualified std::string and the unqualified string resolve to the same type.

If you omitted that using namespace std; directive, you would get a compiler error when using the unqualified string name.

Third problem:

If I use this std::string within a class to declare a private variable, I get an error error: ‘std’ does not name a type. Example of this declaration:

You are missing a colon. That should be:

std::string
//  ^

And not

std:string
// ^