Hello everyone. Just as the title, there is no way to test whether an experession can be ructured bound. The title not looks like a good way and maybe the best idea will come up while discussion.
// These codes are just for learing,
// and the reason why I come up with this idea.
template<class T, class Alloc>
class binary_tree
{
//...
private:
template<
class ValueGetter,
class ChildrenGetter,
class InitializeHandle
>
void recur_and_write_impl(
edge_const_proxy p,
ValueGetter& vg,
ChildrenGetter& cg,
nitializeHandle& h
)
{
if (!p.null())
{
std::unreachable();
}
if (h)
{
emplace(p, std::invoke(vg, h));
auto&& [lh, rh] = std::invoke(cg, h);
auto [l, r] = p.get_children();
recur_and_write_impl(l, vg, cg, lh);
recur_and_write_impl(r, vg, cg, rh);
}
}
public:
binary_tree recur_and_write(
edge_const_proxy p,
ValueGetter vg,
ChildrenGetter cg,
InitializeHandle h
)
{
binary_tree ret{ cut(p) };
recur_and_write_impl(p, vg, cg, h);
return ret;
}
};
The requirement of recur_and_write maybe
requires(auto&& [ lh, rh ] = std::invoke(std::declval<ChildrenGetter>(), std::declval<InitializeHandle>()))
{
(bool)std::declval<InitializeHandle>();
}