[Boost-users] Functions that evaluate to constants

From: Robert Dailey (rcdailey_at_[hidden])
Date: 2008-03-31 12:57:46

Hi,

I realize that C++03 will not permit functions to evaluate down to
compile-time constants. However, I cannot wait until C++0x for this feature.
So, I'm hoping that Boost will allow a temporary solution. Consider the
following structure:

static struct nullptr_t
{
    template< typename t_type >
    operator t_type*() { return 0; }
} nullptr;

The compiler has everything it needs to turn this code into a single
integral constant value. So, if I do the following:

int* foo;
if( foo == nullptr )
{
}

Then it should evaluate down to:

int* foo;
if( foo == 0 )
{
}

Is there any way to provide this behavior in Boost? I would like to avoid
altering the actual design if possible. Perhaps this actually *does*
evaluate to a constant and the problem is that I'm actually unaware of some
specific rule that I didn't find in the C++03 standard. Thanks.