Utilities

template<typename T>
using unwrap_cvref_t = std::remove_cvref_t<std::unwrap_reference_t<T>>

A shorthand type alias that removes std::reference_wrapper, const/volatile and reference qualifiers (in that order) from T.

template<typename IFace, typename T>
concept iface_with_impl

This concept is satisfied if the interface IFace has an implementation for the value type T.

template<typename T>
[[nodiscard]] auto &getval(T *impl)

Type-erased value getter.

This function is intended to be used in an interface implementation in order to access the type-erased value.

If the type-erased value stored in impl is a std::reference_wrapper, this function will unwrap the reference (i.e., it will return a reference to the referenced-to value).

Parameters:

impl – a pointer to an interface implementation.

Returns:

a reference to the type-erased value stored in impl.

Throws:

std::runtime_error – if impl type-erases a const reference and impl is not a const pointer.

template<typename IFace0, typename IFace1, typename ...IFaceN>
struct composite_iface : public IFace0, public IFace1, public IFaceN...

Composite interface.

This class can be used to create a composite interface by multiply inheriting from the interfaces IFace0, IFace1 and IFaceN.

template<typename T>
concept valid_value_type = std::is_object_v<T> && (!std::is_const_v<T>) && (!std::is_volatile_v<T>) && std::destructible<T>

This concept detects if T is a type that can be type-erased by a wrap.

T must be a non-cv qualified destructible object.

template<typename IFace, typename Base, typename Holder, typename T>
struct iface_impl

Non-intrusive interface implementation.

This class can be partially specialised to specify a non-intrusive implementation for the interface IFace. See the tutorial for an example.

The unspecialised version of this class is an empty trivial structure which disables non-intrusive implementations for the interface IFace.