"Gennaro Prota" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> On Thu, 30 Jan 2003 12:38:36 -0000, "John Maddock"
> <[EMAIL PROTECTED]> wrote:
>
> >Except it *doesn't work* !
> >
>
> John, unfortunately I have to turn off my computer now. I had just
> hacked up a version that seems to work with gcc, but I don't want to
> post it before a better testing. I'll let you know in the morning.
Maybe you had the following variation on Terje's code in mind.
The following worked with GCC3.1/2, VC6/7/7.1 and Comeau 4.3.0.1:
typedef char (&yes)[1];
typedef char (&no) [2];
template <typename B, typename D>
struct helper
{
template <typename T>
static yes check(D const volatile *, T);
static no check(B const volatile *, int);
};
template<typename B, typename D>
struct is_base_and_derived
{
struct Host
{
operator B const volatile *() const;
operator D const volatile *();
};
enum { result =
sizeof(helper<B,D>::check(Host(), 0)) == sizeof(yes)
};
};
struct B {};
struct B1 : B {};
struct B2 : B {};
struct D : B1, private B2 {};
struct BV1 : virtual B {};
struct BV2 : virtual B {};
struct DV : BV1, BV2 {};
typedef char TestA[is_base_and_derived<B, D>::result ? 1 : -1]; // Multiple
bases
typedef char TestB[is_base_and_derived<B1,D>::result ? 1 : -1];
typedef char TestC[is_base_and_derived<B2,D>::result ? 1 : -1]; // Private
base
typedef char TestD[!is_base_and_derived<int,D>::result ? 1 : -1];
typedef char TestF[is_base_and_derived<B,DV>::result ? 1 : -1]; // Virtual
base
// VC6/7 BUG.
// typedef char Test[!is_base_and_derived<D,D>::result ? 1 : -1];
Cheers,
Rani
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