I wrote the following class to test when constructors are called for classes on the stack and got an error:

class Test {
  private:
    static int count;
  public:
    Test() {
      cout << "created Test: " << Test::count << endl;
      Test::count++;
    }
};

int main() {
  Test t1;
  Test* t2 = new Test();
}

The error was: undefined reference to Test::count.

Anyone know what the issue is?

You have to put 'int count' somewhere outside the class.

class Test{
...
}
int Test::count;

[edit] slow..

But anyway that code wouldn't count constructors on the stack, you would probably have to redefine the new operator to count the number of dynamically created objects and then do count - dynamic_count.

Ok it will count the constructors on the stack but it won't give you a right answer. The number of objects on the stack is probably also contained in the following:

unsigned int stack_objects = MAXINT;

Anyway, this code seems to work

Then purely stack objects are count - dynamic.

Thanks Jakub and Kazz. Yes, I was just curious in what order constructors where called for static objects, I had the heap allocation in there just because. Turns out they're called in order and in between intevening statements which was a surprise. I assumed all stack objects would be instantiated when the stack frame was allocated, but apparently not so......

cout<< "something" << endl;
Test t1;
cout<< "something 2" << endl;
test t2;

Output:

somthing
created Test 1
something 2
created Test 2

Oh, I guess its the fact that bool does not force a value of 0 or 1 so if one function returned true as 2 and another returned true as 3 then (b1 == b2 ) would be false when the proper test is

if ( b1 != FALSE && b2 != FALSE ){
}

But given the code, I would think that foo and bar would return either TRUE or FALSE anyway..

if(!a == !b)
would work too, for bools and integers, and should be able to be properly optimized by a compiler.

As far as I know, neither. The bool type can only hold two (abstract, non-numeric) values. What C++ does is define an implicit cast from int to bool, which renders any non-zero int as true, and 0 as false. That implicit cast also happens when you use an int in an if or a while.

You can also convert true and false back to int if that is needed, but that will always yield the same value for true (I'm not sure whether it's defined in the standard or left for the implementors to choose).

I just assumed you meant one of the built-in bools because there were no typedefs anywhere. Both C++ bool and the C99 bool are guaranteed to work with your code.

http://dev.fyicenter.com/interview/

Thanks DD!

Tomorrows the day, I'll let you guys know what the questions were.... for the sake of completeness.

Well I just came back from the "interview". It wasn't really an interview, they stuck me in a room with a specification and I wrote some code on paper. If they like it, I'll get called back for a interview with the team.

They had me write a queue using a linked list that stored a Document type that was abstract and I had to extend to two concrete types. I wrote a doubly linked list.

I just remembered, in my haste I added an instance of the abstract class to the queue. Hmmm, maybe I shouldn't plan on getting a call back....

I don't even know what a queue is (In C++ terms..)

I don't think English-as-a-first-language speakers would ever refer to a line up as a queue. Queue is a term I didn't know of until I learned about it in programming terms, although you could use a line up as an example (first come, first served).

Indeed. Queue is used to refer to line ups in the UK all the time. Just watch any BBC show.

A Queue is essentially just a FIFO list.