# std::ranges::lazy_split_view<V, Pattern>::inner_iterator

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< cpp‎ | ranges‎ | lazy split view

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

The return type of `lazy_split_view::outer_iterator::value_type::begin()`.

`Const` matches the template argument of `outer_iterator`.

### Member types

Member type | Definition
`Base` | const V if Const is true, otherwise V (exposition-only member type*)
`iterator_concept` (C++20) | equivalent to /*outer_iterator*/<Const>::iterator_concept, that is std::forward_iterator_tag if `Base` models `forward_range`, or std::input_iterator_tag otherwise.
`iterator_category` (C++20) | Not present if `Base` does not model `forward_range`. std::forward_iterator_tag if std::iterator_traits<ranges::iterator_t<Base>>::iterator_category models std::derived_from<std::forward_iterator_tag>. std::iterator_traits<ranges::iterator_t<Base>>::iterator_category otherwise.
`value_type` (C++20) | ranges::range_value_t<Base>.
`difference_type` (C++20) | ranges::range_difference_t<Base>.

### Data members

Typical implementations of `inner_iterator` hold two non-static data members:

- `i_` (exposition only*) - An iterator of type /*outer_iterator*/<Const> into the underlying `view` of the parent lazy_split_view.
- `incremented_` (exposition only*) - A boolean flag that indicates whether the operator++ was invoked on this object at least once.

### Member functions

(constructor) (C++20) | constructs an iterator (public member function)
base (C++20) | returns the underlying iterator (public member function)
operator* (C++20) | returns the current element (public member function)
operator++operator++(int) (C++20) | advances the iterator (public member function)

### Member functions

## std::ranges::lazy_split_view::inner_iterator::inner_iterator

/*inner_iterator*/() = default; | (1) | (since C++20)
constexpr explicit /*inner_iterator*/( /*outer_iterator*/<Const> i ); | (2) | (since C++20)

1) Value initializes data member `i_` via its default member initializer (= /*outer_iterator*/<Const>()).
2) Initializes `i_` with std::move(i).

The data member `incremented_` is initialized with its default member initializer to false.

## std::ranges::lazy_split_view::inner_iterator::base

constexpr const ranges::iterator_t<Base>& base() const & noexcept; | (1) | (since C++20)
constexpr ranges::iterator_t<Base> base() && requires ranges::forward_range<V>; | (2) | (since C++20)

Returns a copy of the underlying iterator.

1) Copy constructs the result from the underlying iterator. Equivalent to return i_./*cur*/();.
2) Move constructs the result from the underlying iterator. Equivalent to return std::move(i_./*cur*/());.

## std::ranges::lazy_split_view::inner_iterator::operator*

constexpr decltype(auto) operator*() const; |  | (since C++20)

Returns the element the underlying iterator points to.

Equivalent to return *i_./*cur*/();.

## std::ranges::lazy_split_view::inner_iterator::operator++

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

1) The function body is equivalent to
incremented_ = true;

if constexpr (!ranges::forward_range<Base>)
{
if constexpr (Pattern::size() == 0)
return *this;
}
++i_./*cur*/();

return *this;
2) Equivalent to
if constexpr (ranges::forward_range<Base>)

{
auto tmp = *this;
++*this;
return tmp;
}
else
++*this; // no return statement

### Non-member functions

operator== (C++20) | compares the iterators or the iterator and std::default_sentinel (function)
iter_move (C++20) | casts the result of dereferencing the underlying iterator to its associated rvalue reference type (function)
iter_swap (C++20) | swaps the objects pointed to by two underlying iterators (function)

## operator==(std::ranges::split_view::inner_iterator)

friend constexpr bool operator==( const /*inner_iterator*/& x, const /*inner_iterator*/& y ) requires forward_range<Base>; | (1) | (since C++20)
friend constexpr bool operator==( const /*inner_iterator*/& x, std::default_sentinel_t ); | (2) | (since C++20)

1) Equivalent to return x.i_./*cur*/() == y.i_./*cur*/();.
2) The function body is equivalent to

    auto [pcur, pend] = ranges::subrange{x.i_.parent_->pattern_};
    auto end = ranges::end(x.i_.parent_->base_);
    if constexpr (/*tiny_range*/<Pattern>)
    {
        const auto& cur = x.i_./*cur*/();
        if (cur == end)
            return true;
        if (pcur == pend)
            return x.incremented_;
        return *cur == *pcur;
    }
    else
    {
        auto cur = x.i_./*cur*/();
        if (cur == end)
            return true;
        if (pcur == pend)
            return x.incremented_;
        do
        {
            if (*cur != *pcur)
                return false;
            if (++pcur == pend)
                return true;
        }
        while (++cur != end);
        return false;
    }

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::inner_iterator` is an associated class of the arguments.

## iter_move(std::ranges::split_view::inner_iterator)

friend constexpr decltype(auto) iter_move( const /*inner_iterator*/& i ) noexcept(noexcept(ranges::iter_move(i.i_./*cur*/()))); |  | (since C++20)

Equivalent to return ranges::iter_move(i.i_./*cur*/());.

This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when `std::ranges::split_view::inner_iterator` is an associated class of the arguments.

## iter_swap(std::ranges::split_view::inner_iterator)

friend constexpr void iter_swap( const /*inner_iterator*/& x, const /*inner_iterator*/& y ) noexcept(noexcept(ranges::iter_swap(x.i_.current, y.i_.current))) requires std::indirectly_swappable<ranges::iterator_t<Base>>; |  | (since C++20)

Equivalent to ranges::iter_swap(x.i_./*cur*/(), y.i_./*cur*/()).

This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when `std::ranges::split_view::inner_iterator` is an associated class of the arguments.

### Defect reports

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

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 3591 | C++20 | the && overload of `base` might invalidate outer iterators | constraints added
LWG 3593 | C++20 | the const& overload of `base` returns a reference but might not be noexcept | made noexcept

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