25 Iterators library [iterators]

To implement algorithms taking projections, it is necessary to determine the projected type of an iterator's value type.

For the exposition-only alias template indirect-value-t, indirect-value-t<T> denotes

• (1.1)
  invoke_result_t<Proj&, indirect-value-t<I>> if T names projected<I, Proj>, and
• (1.2)
  iter_value_t<T>& otherwise.