std::ranges...er_iterator(3)

💅 std::ranges...er_iterator(3) — C++ Standard Libary 💅

okay bestie, welcome to std::ranges...er_iterator(3) from the C++ Standard Libary manual. this page is literally all about the exposition-only outer iterator for lazy_split_view, and yes it has lore ✨

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🌸 NAME 🌸

std::ranges::lazy_split_view::outer_iterator — that's it, that's the name: std::ranges::lazy_split_view::outer_iterator 💖

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✨ SYNOPSIS ✨

template< bool Const >        (since C++20)
struct /* outer_iterator */;  (exposition only*)

This is the return type of lazy_split_view::begin, and of lazy_split_view::end when the underlying view is a common_range and forward_range.

If either V or Pattern is not a simple view (e.g. if ranges::iterator_t<const V> is invalid or different from ranges::iterator_t<V>), Const is true for iterators returned from the const overloads, and false otherwise. If V is a simple view, Const is true if and only if V is a forward_range.

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🎀 MEMBER TYPES 🎀

• Parent — const ranges::lazy_split_view if Const is true, otherwise ranges::lazy_split_view (exposition-only member type*)
• Base — const V if Const is true, otherwise V (exposition-only member type*)
• iterator_concept (C++20) — std::forward_iterator_tag if Base models forward_range, otherwise std::input_iterator_tag
• iterator_category (C++20) — std::input_iterator_tag if Base models forward_range. Not present otherwise.
• value_type (C++20) — ranges::lazy_iterator_view<V, Pattern>::/* outer_iterator */<Const>::value_type
• difference_type (C++20) — ranges::range_difference_t<Base>.

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🦋 DATA MEMBERS 🦋

• parent_ (private) — A pointer of type Parent* to the parent lazy_split_view object (exposition-only member object*)
• current_ (private) — An iterator of type ranges::iterator_t<Base> into the underlying view; present only if V models forward_range (exposition-only member object*)
• trailing_empty_ (private) — A boolean flag that indicates whether an empty trailing subrange (if any) was reached (exposition-only member object*)

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💜 MEMBER FUNCTIONS 💜

• constructor (C++20) — constructs an iterator (public member function)
• operator* (C++20) — returns the current subrange (public member function)
• operator++, operator++(int) (C++20) — advances the iterator (public member function)
• cur (C++20) — returns conditionally a reference to the current_ (if present) or to the *parent_->current_ (exposition-only member function*)

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💖 MEMBER FUNCTIONS: std::ranges::lazy_split_view::outer_iterator ::outer_iterator 💖

1. /* outer_iterator */() = default; — (since C++20)
2. constexpr explicit /* outer_iterator */( Parent& parent ) — (since C++20) with requires (!ranges::forward_range<Base>);
3. constexpr /* outer_iterator */( Parent& parent, ranges::iterator_t<Base> current ) — (since C++20) with requires ranges::forward_range<Base>;
4. constexpr /* outer_iterator */( /* outer_iterator */<!Const> i ) — (since C++20) with requires Const && std::convertible_to<ranges::iterator_t<V>, ranges::iterator_t<Base>>;

1) Value initializes the non-static data members with their default member initializer, that is:

• parent_ = nullptr;
• current_ = iterator_t<Base>(); (present only if V models forward_range),

2) Initializes parent_ with std::addressof(parent).

3) Initializes parent_ with std::addressof(parent) and current_ with std::move(current).

4) Initializes parent_ with i.parent_, current_ with std::move(i.current_), and trailing_empty_ with t.trailing_empty_.

The trailing_empty_ is initialized with its default member initializer to false.

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🌈 MEMBER FUNCTIONS: std::ranges::lazy_split_view::outer_iterator ::operator* 🌈

constexpr value_type operator*() const;  (since C++20)

Equivalent to return value_type{*this};. slay, short and iconic 💅

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🔥 MEMBER FUNCTIONS: std::ranges::lazy_split_view::outer_iterator ::operator++ 🔥

constexpr /* outer_iterator */& operator++(); (1) (since C++20)
constexpr decltype(auto) operator++(int);     (2) (since C++20)

1) The function body is equivalent to:

const auto end = ranges::end(parent_->base_);
if (/* cur */() == end)
{
    trailing_empty_ = false;
    return *this;
}
const auto [pbegin, pend] = ranges::subrange{parent_->pattern_};
if (pbegin == pend)
    ++/* cur */();
else if constexpr (/* tiny_range */<Pattern>)
{
    /* cur */() = ranges::find(std::move(/* cur */()), end, *pbegin);
    if (/* cur */() != end)
    {
        ++/* cur */();
        if (/* cur */() == end)
            trailing_empty_ = true;
    }
}
else
{
    do
    {
        auto [b, p] = ranges::mismatch(/* cur */(), end, pbegin, pend);
        if (p == pend)
        {
            /* cur */() = b;
            if (/* cur */() == end)
                trailing_empty_ = true;
            break; // The pattern matched; skip it
        }
    } while (++/* cur */() != end);
}
return *this;

2) Equivalent to:

if constexpr (ranges::forward_range<Base>)
{
    auto tmp = *this;
    ++*this;
    return tmp;
}
else
{
    ++*this; // no return statement
}

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🧚 MEMBER FUNCTIONS: std::ranges::lazy_split_view::outer_iterator ::cur () 🧚

constexpr auto& /* cur */() noexcept;       (1) (since C++20)
                                                (exposition only*)
constexpr auto& /* cur */() const noexcept; (2) (since C++20)
                                                (exposition only*)

This convenience member function is referred to from /* outer_iterator */::operator++(), from the non-member operator==(const /* outer_iterator */&, std::default_sentinel_t), and from some member functions of the possible implementation of inner_iterator.

1,2) Equivalent to:

if constexpr (ranges::forward_range<V>)
    return current_;
else
    return *parent->current_;

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⭐ NON-MEMBER FUNCTIONS ⭐

• operator== (C++20) — compares the underlying iterators or the underlying iterator and std::default_sentinel (function)

🌟 operator==(std::ranges::split_view::outer_iterator) 🌟

friend constexpr bool operator==( const /* outer_iterator */& x,
                                  const /* outer_iterator */& y )

(1) (since C++20) requires forward_range<Base>;

friend constexpr bool operator==( const /* outer_iterator */& x,
                                  std::default_sentinel_t );

(2) (since C++20)

1) Equivalent to return x.current_ == y.current_ and x.trailing_empty_ == y.trailing_empty_;.

2) Equivalent to return x./* cur */() == ranges::end(x.parent_->base_) and !x.trailing_empty_;.

The != operator is synthesized from operator==.

These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::ranges::split_view::outer_iterator is an associated class of the arguments. no cap, that ADL note matters 👑

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🌸 NESTED CLASSES 🌸

• value_type (C++20) — the value type of the outer_iterator (public member class)

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💀 DEFECT REPORTS 💀

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

• DR LWG 3904, applied to C++20 — as published: trailing_empty_ was not initialized in constructor overload (4); correct behavior: initialized.

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that's the whole page bestie 🫶 source: http://cppreference.com; version/date: 2024.06.10; page: std::ranges...er_iterator(3). periodt ✨