Doesn't show the overloading part, but that's OK.
Quick question: Given the ability to return different (necessarily related?) types from the same open-method, can we say BOM allows co-variant return type? Like virtual methods / polymorphism allows, just more flexible that plain pointers?
Yes. And in that case, the return type can act as a tie-breaker, as described in N2216. Here is `transpose` with `const` and covariant return types: BOOST_OPENMETHOD( transpose, (shared_virtual_ptr<const Matrix>), shared_virtual_ptr<const Matrix>); BOOST_OPENMETHOD_OVERRIDE( transpose, (shared_virtual_ptr<const OrdinaryMatrix>), shared_virtual_ptr<const OrdinaryMatrix>) { return make_shared_virtual<OrdinaryMatrix>(); } BOOST_OPENMETHOD_OVERRIDE( transpose, (shared_virtual_ptr<const SymmetricMatrix> m), shared_virtual_ptr<const SymmetricMatrix>) { return m; } You can call a specific overrider like so: auto u = BOOST_OPENMETHOD_OVERRIDERS( transpose)<shared_virtual_ptr<const SymmetricMatrix>( shared_virtual_ptr<const SymmetricMatrix>)>::fn(m); static_assert( std::is_same_v<decltype(u), shared_virtual_ptr<const SymmetricMatrix>>); (Compiler Explorer: https://godbolt.org/z/ndKaKWPzd) J-L On Tue, Mar 11, 2025 at 4:59 AM Dominique Devienne <ddevienne@gmail.com> wrote:
On Mon, Mar 10, 2025 at 9:45 PM Jean-Louis Leroy via Boost <boost@lists.boost.org> wrote:
[...] handling of const-ness `const` is supported.
Doesn't show the overloading part, but that's OK.
Quick question: Given the ability to return different (necessarily related?) types from the same open-method, can we say BOM allows co-variant return type? Like virtual methods / polymorphism allows, just more flexible that plain pointers?
Thanks, --DD