23 Iterators library [iterators]

23.3 Iterator requirements [iterator.requirements]

23.3.7 Common algorithm requirements [alg.req]

23.3.7.2 Concept indirectly_­movable [alg.req.ind.move]

The indirectly_­movable concept specifies the relationship between a readable type and a writable type between which values may be moved.
template<class In, class Out>
  concept indirectly_movable =
    readable<In> &&
    writable<Out, iter_rvalue_reference_t<In>>;
The indirectly_­movable_­storable concept augments indirectly_­movable with additional requirements enabling the transfer to be performed through an intermediate object of the readable type's value type.
template<class In, class Out>
  concept indirectly_movable_storable =
    indirectly_movable<In, Out> &&
    writable<Out, iter_value_t<In>> &&
    movable<iter_value_t<In>> &&
    constructible_from<iter_value_t<In>, iter_rvalue_reference_t<In>> &&
    assignable_from<iter_value_t<In>&, iter_rvalue_reference_t<In>>;
Let i be a dereferenceable value of type In.
In and Out model indirectly_­movable_­storable<In, Out> only if after the initialization of the object obj in
iter_value_t<In> obj(ranges::iter_move(i));
obj is equal to the value previously denoted by *i.
If iter_­rvalue_­reference_­t<In> is an rvalue reference type, the resulting state of the value denoted by *i is valid but unspecified ([lib.types.movedfrom]).