The IndirectlyCopyable concept specifies the relationship between a Readable type and a Writable type between which values may be copied.
template <class In, class Out> concept bool IndirectlyCopyable = Readable<In> && Writable<Out, reference_t<In>>;
The IndirectlyCopyableStorable concept augments IndirectlyCopyable with additional requirements enabling the transfer to be performed through an intermediate object of the Readable type's value type. It also requires the capability to make copies of values.
template <class In, class Out> concept bool IndirectlyCopyableStorable = IndirectlyCopyable<In, Out> && Writable<Out, const value_type_t<In>&> && Copyable<value_type_t<In>> && Constructible<value_type_t<In>, reference_t<In>> && Assignable<value_type_t<In>&, reference_t<In>>;