Thread: is it fine to assign zero(0) to a string object, in any case?

It is not possible to assign 0 to a string object, since it is an integer, not a string.
Also note that it is called "string", not "String", as C++ is case sensitive.
Furthermore, take care not to begin names with _, since they are usually reserved for language implementations.

However, the following example compiles:

Code:

#include <string>

int main()
{
    std::string s = 0;

}

It is equivalent to

Code:

std::string s((char*)0);

but the result, I'm afraid, is undefined (GCC throws an exception).

Originally Posted by Alexpo

And would you pls, let me know where can i find more precise technical info about "how java is 2 step back and 1 step forward" mentioned in the quote of ur post.

It is more of an opinion than actual fact. I know of maybe a few things in Java that is worse than C++ (again, opinion). No real technical facts.

Underscores are not particularly fine, either, as they are discouraged on the forum.
Use underscores for library implementations and such (not two underscores), and not in normal code. I believe that is the suggested advice.

The rule on underscores is:

No double underscores anywhere in the name. No single underscore followed by a capital letter at the start of a name. No single underscore to start the name if it is in the global namespace.

Since it is obviously difficult for people to remember the exact rules, a simpler version is no double underscores and no single underscores to start the name. That way you'll be safe.


As to assigning 0 to a string or initializing it with 0, it's wrong. The standard states that when initializing a string with a char* pointer, the pointer shall not be null. So if you do initialize it with 0, you will get undefined behavior.

Note that it is possible that in the Lippman book you refer to, he is using a different string class than the standard string class (which might be why it is referred to as String instead of string). If that's the case, then that String class might allow 0 to be passed to its constructor, but there's no way to know without looking at the book.