Programming Forums - std::string is not empty?

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std::string is not empty?

Is the std::string empty - or not?
If we check a string like this

std::string myStr;



if(myStr.empty())

    std::cout << "The string is empty" << std::endl;

else

    std::cout << "The string is not empty" << std::endl;

It of course returns the first message, but if we do like this

for(int i = 0; i <= 50; i++)

{

    if(static_cast<int>(myStr[i]) != 0)

        std::cout << "Index[" << i << "] = " << static_cast<int>(myStr[i]) << std::endl;

}

Then there's is some of them with content. On my computer I get the output

Quote:

Originally Posted by Output

Index[4] = 7
Index[8] = 8
Index[12] = 11
Index[16] = 6
Index[20] = 4
Index[24] = 5
Index[28] = 14
Index[32] = 3
Index[36] = 12
Index[40] = 13
Index[44] = 9
Index[48] = 10

As we can see it jumps four, before it's contains content, why?
How can I competely clear the string? I've tried clear() but it again returns some strange content. I've to clear the string competely, because I've to do actions like myStr[2]++ on empty strings, and it's hard if it contains something...

// This is how it should be...

// myStr[4] = 0;

myStr[4]++;

// myStr[4] = 1;



// This is how it is now...

// myStr[4] = 7;

myStr[4]++;

// myStr[4] = 8;

I've found another solution.
Instead of using an std::string for data, I now use a std::vector.

Hi v0id, the internal format of a std::string is not specified specifically so you cannot rely on something like say an empty string being 'zero'ed unfortunately. In addition I suspect trying to access index's outside the strings length is very dangerous.

I would advise designing your own simple string class based on your needs, perhaps one which you could convert to and from std::strings as you need. You could use something like std::vector<char> for the memory which would mean you'd know exactly what is going on beneath the surface.

[edit] you beat me to the answer :)

Quote:

Originally Posted by Eoin

In addition I suspect trying to access index's outside the strings length is very dangerous.

It was exactly because of this reason I choosed a container instead. I'd been on the wrong track all the time, because it was only data I should store, not a specific string - to output, eg.

Thanks for your time and answer. :-)

Whats the size() for?

size () is for the size of the string, in characters. It has nothing to do with the size of the class, per se, which has a number of controlling entities. A study (or design) of containers would probably clear up some unwarranted misconceptions.