Re: typetraits of STL containers and iterators

I've never used boost::type_traits personally, but I would think it
would work. Not sure though. If not, you could define a template and
then specialize accordingly. I gave it a try, thinking most STL
iterators would be derived from std::iterator:

#include <iterator>

template < typename Type >
struct is_iterator_type
{
    enum { value = false };
};

template < class Category, class Type, class Distance, class Pointer,
class Reference >
struct is_iterator_type< std::iterator< Category, Type, Distance,
Pointer, Reference > >
{
    enum { value = true };
};

template < typename Type >
struct is_iterator_type< Type* >
{
    enum { value = true };
};

template < typename Type >
struct is_iterator_type< Type const* >
{
    enum { value = true };
};

/*
    Helper function that deduces the type of some value
*/
template < typename Type >
inline bool is_iterator( Type const& )
{
    return is_iterator_type< Type >::value;
}

// Test:

#include <cassert>
#include <list>
#include <vector>

int main( void )
{
    using namespace
        std;
    char*
        pc = 0;
    char const*
        pcc = 0;
    char const* const
        pccc = 0;
    list< char >
        lc;
    vector< char >
        vc;
    assert( is_iterator( pc ) );
    assert( is_iterator( pcc ) );
    assert( is_iterator( pccc ) );
    assert( is_iterator( lc.begin( ) ) );
    assert( is_iterator( vc.rbegin( ) ) );
    return 0;
}

Unfortunately, the assertion failed on the container iterators. So you
would need to specialize is_iterator_type for every possibility. And
as far as detected a container type, again, neither do these have a
common base class, so you would have to define and specialize a
template for every know type.

- hth