Concept Subspace :: sus :: iter :: DoubleEndedIterator

source
template <class T, class Item = typename std::remove_cvref_t<T>::Item>
concept DoubleEndedIterator
requires 
sus::iter::Iterator<T, Item>
requires(std::remove_cvref_t<T>& t) {
      { t.next_back() } noexcept -> std::same_as<::sus::option::Option<Item>>;
    }

An Iterator able to yield elements from both ends.

Something that implements DoubleEndedIterator has one extra capability over something that implements Iterator: the ability to also take Items from the back, as well as the front.

It is important to note that both back and forth work on the same range, and do not cross: iteration is over when they meet in the middle.

In a similar fashion to the Iterator protocol, once a DoubleEndedIterator returns None from a next_back(), calling it again may or may not ever return Some again. next() and next_back() are interchangeable for this purpose.

Required methods.

A DoubleEndedIterator has one required methods, in addition to those required by Iterator.

  • auto next_back() -> Option<Item> returns an Option containing the next Item from the back of the iterator as long as there are elements, and once they've all been exhausted, will return None to indicate that iteration is finished.