Thorsten Ottosen wrote:
I was messing around with enable_if to see if we could detect the number of
arguments. But I couldn't find a traits that does that yesterday ... now I
see
could help. This way I think we can avoid instantiating result_of until it
works.
Note that you cannot use SFINAE based on template `Fun`'s arity
since `Fun` is not a template parameter of void_ptr_indirect_fun's operator().
To avoid unnecessary instanciation of result_of,
we might need to make operator() a function template and
make its return type a dependent type of its template parameters.
The following code works fine:
#include
#include
/* ... */
template
struct make_lazy
{
typedef typename Type::type type;
};
template
class void_ptr_indirect_fun
{
/* ... */
template <typename Dummy>
typename make_lazy<
boost::result_of
, Dummy
>::type
operator()(const Dummy* r) const
{
BOOST_STATIC_ASSERT(boost::is_void<Dummy>::value);
BOOST_ASSERT(r != 0);
return fun(
*static_cast(static_cast(r))
);
}
template <typename Dummy>
typename make_lazy<
boost::result_of
, Dummy
>::type
operator()(const Dummy* l, const Dummy* r) const
{
BOOST_STATIC_ASSERT(boost::is_void<Dummy>::value);
BOOST_ASSERT(l != 0 && r != 0);
return fun(
*static_cast(static_cast(l))
, *static_cast(static_cast(r))
);
}
/* ... */
};
/* ... */
Regards,
Michel
