std::ranges...erator++,--(3)

💖 NAME 💖

std::ranges::join_with_view::iterator::operator++,-- — aka std::ranges::join_with_view::iterator::operator++,--. We're in the C++ Standard Libary manual, section 3, bestie, and this page is all about the increment and decrement operators. 💅

✨ Synopsis ✨

          constexpr /*iterator*/& operator++();                  (1) (since
       C++23)
          constexpr void operator++( int );                      (2) (since
       C++23)
          constexpr /*iterator*/ operator++( int )

            requires std::is_reference_v<InnerBase> &&           (3) (since
       C++23)
                     ranges::forward_range<Base> &&

                     ranges::forward_range<InnerBase>;
          constexpr /*iterator*/& operator--()

            requires std::is_reference_v<InnerBase> &&
                     ranges::bidirectional_range<Base> &&
                     ranges::bidirectional_range<InnerBase> &&   (4) (since
       C++23)
                     ranges::common_range<InnerBase> &&
                     ranges::bidirectional_range<PatternBase> &&

                     ranges::common_range<PatternBase>;
          constexpr /*iterator*/ operator--( int )

            requires std::is_reference_v<InnerBase> &&
                     ranges::bidirectional_range<Base> &&
                     ranges::bidirectional_range<InnerBase> &&   (5) (since
       C++23)
                     ranges::common_range<InnerBase> &&
                     ranges::bidirectional_range<PatternBase> &&

                     ranges::common_range<PatternBase>;

All of these overloads are since C++23, periodt. The requires-clauses are doing a lot, so read them like your fave’s outfit details: every line matters. 💜

Okay so, real talk: this whole page is literally about incrementing or decrementing the iterator. Here’s the overload-by-overload tea, no cap:

1. (1) operator++() increments the stored inner iterator. That inner iterator may point to either InnerBase or PatternBase — iykyk.
   • If the incremented inner iterator reaches the end of the pattern range, it is destroyed, and an iterator to the beginning of the next inner range is constructed. 🫶
   • If the incremented inner iterator reaches the end of the inner range, the outer iterator is incremented, and if the outer iterator is not the end iterator, the inner iterator is destroyed and an iterator to the beginning of the pattern range is constructed.
   • The above steps may be repeated (e.g. if the pattern is empty), until either the inner range is not empty, or the outer iterator reaches the end. Slay.
2. (2) operator++( int ) is equivalent to ++*this;
3. (3) operator++( int ) is equivalent to auto tmp = *this; ++*this; return tmp;
4. (4) operator--(): If the outer iterator is the end iterator, it is decremented. Then:
   • If the stored inner iterator refers to the beginning of the inner range, it is destroyed, and an iterator to the end of the pattern range is constructed.
   • If the stored inner iterator refers to the beginning of the pattern range, it is destroyed, the outer iterator is decremented, and an iterator to end of the inner range is constructed.
   • The above steps may be repeated (e.g. if the pattern is empty), until the inner range is not empty.

Finally, the inner iterator is decremented. 💅

5. (5) operator--( int ) is equivalent to auto tmp = *this; --*this; return tmp;

If InnerBase is not a reference, the inner range is stored in the parent join_with_view for iteration. The inner range need not be movable. Lowkey important.

If InnerBase is a reference, and the outer iterator reaches the end, the inner iterator points to the beginning of the pattern range. That’s the rule, fr fr.

🫶 Parameters 🫶

(none) — literally none, bestie.

🎀 Return value 🎀

• 1,4) *this
• 3,5) A copy of *this that was made before the change.

Okay that’s the whole page, bestie. Source/version shoutout: http://cppreference.com; date: 2024.06.10. Mwah 💋✨