mark++

I’ve had a minor revelation since my last two posts about C++. I don’t actually need the new auto keyword. Check it out:

#include 
#include 
#include 

using namespace std;
using namespace boost;

void hello( int a )
{
    while( a– ) cout << "Hi Mom: " << a << endl;
}
int main()
{
    const int count = 5;
    function< void (void) > func = bind( hello, count );
    func();
}

I’m still not exactly sure how this works, but I’m positve that boost::function rocks.

I’ve been thinking about my C++ problem.

I initially expected the return type of the bind expression would be void (*)(void). Obviously (well, it’s obvious now, anyway), this is not what bind returns. Rather, bind returns a function object (aka, a functor). A functor is just an object that implements operator(), making itself a “callable entity”. In my case, bind is returning a functor which implements void operator()(void) — which is similar, but not quite the same as a “nullary” function pointer void (*)(void).

So, what’s the type of the functor? Turns out it’s:


class boost::_bi::bind_t > >


Couldn’t be simpler than that, eh? How do I know this? The compiler tells me the type when it errors-out during compilation. And that is the most frustrating thing of all. The compiler knows the damn type, but there is no way for me to tell it, “Yes, yes! Just use one of those, thanks.”

At least, not until we get Dave Abraham’s new auto keyword.