Thread: How get bool's from std::vector<bool>

I don't know how many people know this but a vector of bools is not a container. (see this: http://www.gotw.ca/publications/mill09.htm for more info)

I have a template'd function that works for everything except a vector of bools (again read the article to see why).

Code:

//My function is essentially like this
template<class T>
void f( T& t )
{
    //Neither of these two statements work with bool
    typename T::value_type* p1 = &t[0];
    typename T::value_type* p2 = &*t.begin();

    // ... do something with *p1 and *p2 ...
}

So my question is: what's the best way to get the data from a vector of bools? Is the only way to loop through it and do it one item at a time?

I tried:

#define STD_VECTOR_BOOL_NOT_SPECIAL

but that didn't do anything (using g++ 3.4.5).

Is there a reason you need it to work with a vector<bool>?

I don't believe you can get the data out as an array.

Originally Posted by CornedBee

You cannot get the data as an array, because the data is not there.

Yeah, I'm gonna have to force it to be a vector of chars instead.

Have you considered using std::basic_string<bool> instead?
Having the word "string" in the name is obviously confusing, but I believe it should provide functionality that's pretty similar to a vector.
Scott Meyers seems to agree with my suggestion and included it on his Book Errata list for "Effective STL" http://aristeia.com/BookErrata/estl1...ta_frames.html (search for "cpj").

or a deque<bool>