## vptr_map

### Synopsis

```c++
namespace boost::openmethod::policies {

### Synopsis

template<class Policy, class MapAdaptor = mp11::mp_quote<std::unordered_map>>
class vptr_map : public extern_vptr {
  public:
    template<typename ForwardIterator>
    static auto register_vptrs(ForwardIterator first, ForwardIterator last) -> void;

    template<class Class>
    static auto dynamic_vptr(const Class& arg) -> const vptr_type&;
};

}
```

### Description

`vptr_map` is an implementation of `external_vptr that stores the pointers to
the v-tables in a map. If `Policy` contains `indirect_vptr`, a level of
indirection is added, making the policy usable in presence of dynamic loading.

`Policy` is the policy containing the policy.

`MapAdaptor` is a Boost.Mp11 quoted metafunction that returns a map type.

### Members

#### register_vptrs

```c++
template<typename ForwardIterator>
auto register_vptrs(ForwardIterator first, ForwardIterator last) -> void;
```

Stores the pointers to v-tables in a _Map_.

#### dynamic_vptr

```c++
template<class Class>
auto dynamic_vptr(const Class& object) -> const vptr_type&;
```

Returns a pointer to the v-table for `object` (by reference).

If _Policy_ contains the `runtime_checks` policy, checks if _Class_ is
registered. If it is not, and _Policy_ contains a `error_handler` policy, calls
its `error` function; then calls `abort`.