std::experi...or_category(3)

💖 NAME 💖

std::experimental::ranges::iterator_category — ok so this whole page is about that, bestie, it's std::experimental::ranges::iterator_category fr fr 💅

(this lives in the C++ Standard Libary manual, yes that's the manual's name, no I'm not fixing the spelling, it's iconic 😭)

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✨ Synopsis ✨

It's defined in the header <experimental/ranges/iterator>, periodt:

template< class I >                                          (1)
struct iterator_category {};

template< class T >                                          (2)
struct iterator_category<T*>;

template< class T >                                          (3)
struct iterator_category<const T> : iterator_category<T> {};

template< class T >
    requires requires { typename T::iterator_category; }     (4)
struct iterator_category<T>;

So what does it even do 👀 — it computes the iterator category of the class I, if any. And yes, users may specialize iterator_category for a program-defined type. Go off, customize away 🫶

The four flavors:

1. The primary template is an empty struct. That's it. Empty. Nothing inside. A little void where a heart should be 💀
2. This one's the specialization for pointers. If T is an object type, it provides a member type type equal to ranges::random_access_iterator_tag. Otherwise? There is no member type. Tough luck 🙈
3. Specialization for const-qualified types.
4. Specialization for types that define a public and accessible member type iterator_category. If T::iterator_category is the same as or derived from one of the iterator category tags in namespace std, it gets mapped to the corresponding tag in the namespace ranges, as described down below ⬇️. Otherwise, it provides a member type type equal to T::iterator_category.

And here's the mapping tea ☕ (this is the "as described below" part, you're welcome):

• If T::iterator_category is the same as or derives from std::random_access_iterator_tag, it provides a member type type equal to ranges::random_access_iterator_tag. 🏃‍♀️💨
• Otherwise, if T::iterator_category is the same as or derives from std::bidirectional_iterator_tag, it provides a member type type equal to ranges::bidirectional_iterator_tag. ↔️
• Otherwise, if T::iterator_category is the same as or derives from std::forward_iterator_tag, it provides a member type type equal to ranges::forward_iterator_tag. ➡️
• Otherwise, if T::iterator_category is the same as or derives from std::input_iterator_tag, it provides a member type type equal to ranges::input_iterator_tag. 📥
• Otherwise, if T::iterator_category is the same as or derives from std::output_iterator_tag, there is no member type. 📤🚫

🎀 Helper alias template 🎀

Also there's this little cutie, from the (ranges TS):

template< class T >
using iterator_category_t = typename ranges::iterator_category<T>::type;

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🌸 Example 🌸

This section is incomplete. Reason: no example.

No example, bestie. None. Zero. It's giving "trust me bro" 😭 The page literally says so, I'm not hiding anything from you.

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🦋 See also 🦋

• input_iterator_tag
• output_iterator_tag
• forward_iterator_tag
• bidirectional_iterator_tag
• random_access_iterator_tag
• contiguous_iterator_tag (C++20)

…all of those are empty class types used to indicate iterator categories (they're (class) types, ngl). 💫

• iterator_traits — the compatibility traits class that collects an iterator's associated types (the page also chucks an (alias template) label down here with it 🙈).

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🍓 Category 🍓

• Todo no example 😔

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ok that's the whole page, you ate that 💅✨ — this was std::experi...or_category(3) from http://cppreference.com, dated 2024.06.10. mwah, go read some more manpages bestie 🎀💖🫶