Am 14.03.21 um 18:33 schrieb Peter Dimov via Boost:
mod_virtual is necessary for the implementation of mod_inherited for base
classes (virtual bases of the same type must only be returned once.)
Since the library has to compute it anyway, I might as well return it to the user.
My original design (which was about a compiler implementation of these
reflection facilities) had more such output-only "modifiers", such as mod_final
and mod_overridden. These, along with mod_virtual, were supposed to
be returned in member function descriptors - the compiler knows all this and
we can't get it in any other way, so why not return it. In the library
implementation, only mod_virtual for bases remained. :-)
This reminds me of a question I had earlier but forgot: Given C++17
constexpr if I think it would be useful to return ALL members and then
constexpr if on the type.
E.g. currently it is not possible to do:
boost::mp11::mp_for_each>([&](auto D){
if constexpr(is_function(D)) handle_function
if constexpr(is_variable(D)) handle_variable
}
I think the situation where this would be most useful is:
boost::mp11::mp_for_each>([&](auto D){
some_computation
// use the result of the computation to call functions which may be
static
if constexpr(is_static(D)) handle_static_function
else handle_member_function
}
I.e. the problem with the toggles is, that they are toggles only. It is
impossible to return both static and not-static members, which
especially for functions is useful
In general it is impossible to return ALL members, e.g.
`boost::mp11::mp_for_each` could be useful,
especially for a compiler implementation
Also a reminder that those toggles should stand out. E.g. I was
wondering whether mod_hidden meant, that only hidden members are
returned or in addition. :)
Just thinking out loud: `describe_members` and `describe_members` could work too and make that clear if those
are kept as toggles.
