deductiongu...es::subrange(3)

🌸 NAME 🌸

okay bestie, this is the manual page for deductiongu...es::subrange(3) from the C++ Standard Libary — yes, that's the header's spelling, not mine 💀. The NAME line is literally deductionguidesforstd::ranges::subrange — deductionguidesforstd::ranges::subrange. no cap, that's the whole name. 💅

✨ Synopsis ✨

Defined in header <ranges>

(1) (since C++20)

template< std::input_or_output_iterator I, std::sentinel_for<I> S >
subrange(I, S) -> subrange<I, S>;

(2) (since C++20)

template< std::input_or_output_iterator I, std::sentinel_for<I> S >
subrange(I, S, /*make-unsigned-like-t*/<std::iter_difference_t<I>>)
  -> subrange<I, S, ranges::subrange_kind::sized>;

(3) (since C++20)

template< ranges::borrowed_range<R> >
subrange(R&&) ->
  subrange<ranges::iterator_t<R>, ranges::sentinel_t<R>,
           (ranges::sized_range<R> ||
            std::sized_sentinel_for<ranges::sentinel_t<R>, ranges::iterator_t<R>>) ?
             ranges::subrange_kind::sized :
             ranges::subrange_kind::unsized>;

(4) (since C++20)

template< ranges::borrowed_range<R> >
subrange(R&&, /*make-unsigned-like-t*/<ranges::range_difference_t<R>>) ->
  subrange<ranges::iterator_t<R>, ranges::sentinel_t<R>,
           ranges::subrange_kind::sized>;

These deduction guides are provided for std::ranges::subrange. 🫶

1. Deduces the template arguments from the type of iterator and sentinel. The subrange is sized if std::sized_sentinel_for<S, I> is satisfied, as determined by the default template argument.
2. Deduces the template arguments from the type of iterator and sentinel, while the size of range is specified. The subrange is always sized.
3. Deduces the template arguments from the type of range. The subrange is sized if the size can be obtained from the range or its iterator and sentinel.
4. Deduces the template arguments from the type of range, while the size of range is specified. The subrange is always sized.

The exposition-only alias template make-unsigned-like-t maps each integer-like type to its corresponding unsigned version. ✨

👑 Notes 👑

While constructing the subrange object, bestie:

• for (1,2), the behavior is undefined if the iterator-sentinel pair does not denote a valid range,
• for (2,4), the behavior is undefined if the given size is not equal to the size of the range.

undefined behavior is not a vibe 😭 please respect the valid range and the size, fr fr.

🎀 Example 🎀

This section is incomplete Reason: no example

🦋 Defect reports 🦋

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

• DR: LWG 3404
  • Applied to: C++20
  • Behavior as published: meaningless deduction guides from pair-like types were provided
  • Correct behavior: removed

🍓 Category 🍓

• * Todo no example

---

okay that's the whole manual page, bestie 💖 — it lives at http://cppreference.com, dated 2024.06.10, and the footer label is deductiongu...es::subrange(3). go off, deduction guides, periodt. 🌈✨