etl/docs/iterators/circular_iterator.md

title
circular_iterator

{{< callout type="info">}} Header: circular_iterator.h
Since: 20.34.0
{{< /callout >}}

An iterator wrapper where increments and decrements will roll around the boundaries of an iterator range.
It is constructed with the begin and end of the range, plus an optional start position.
May be used with forward, bidirectional and random access iterators.

template <typename TIterator>
etl::circular_iterator final;

Types

value_type
difference_type
pointer
reference
iterator_category

Constructors

ETL_CONSTEXPR14 circular_iterator()

Default constructor.

---

ETL_CONSTEXPR14 circular_iterator(TIterator itr_begin, TIterator itr_end)

Construct from iterators.

---

ETL_CONSTEXPR14 circular_iterator(TIterator itr_begin, TIterator itr_end, TIterator itr_start)

Construct from iterators and start position

---

ETL_CONSTEXPR14 circular_iterator(const circular_iterator& other)

Copy constructor

Member functions

ETL_CONSTEXPR14 circular_iterator& operator =(const circular_iterator& other)

Assignment operator

---

ETL_CONSTEXPR14 size_t size() const

Returns the length of the range.

---

ETL_CONSTEXPR14 bool empty() const

Returns true if the range is empty.

---

ETL_CONSTEXPR14 value_type operator *()

Dereference operator

---

ETL_CONSTEXPR14 const value_type operator *() const

Dereference operator

---

ETL_CONSTEXPR14 TIterator operator ->()

-> operator

---

ETL_CONSTEXPR14 const TIterator operator ->() const

-> operator

---

ETL_CONSTEXPR14 operator TIterator() const

Conversion operator

---

ETL_CONSTEXPR14 TIterator current() const

Conversion to the base iterator type

---

ETL_CONSTEXPR14 circular_iterator& operator ++()

Increment
Forward iterator
Bidirectional iterator
Random access iterator

---

ETL_CONSTEXPR14 circular_iterator operator ++(int)

Increment
Forward iterator
Bidirectional iterator
Random access iterator

---

ETL_CONSTEXPR14 circular_iterator& operator --()
``
Decrement  
Bidirectional iterator  
Random access iterator  

---

```cpp
ETL_CONSTEXPR14 circular_iterator operator --(int)

Decrement
Bidirectional iterator
Random access iterator

---

ETL_CONSTEXPR14 circular_iterator& operator +=(difference_type offset)

+= operator
Random access iterator

---

ETL_CONSTEXPR14 circular_iterator& operator -=(typename 
                                               etl::iterator_traits<TIterator>::difference_type 
                                               offset)

-= operator Random access iterator

Non-member functions

template <typename TIterator>
ETL_CONSTEXPR14 
typename etl::iterator_traits<TIterator>::difference_type 
operator - (etl::circular_iterator<TIterator>& lhs, etl::circular_iterator<TIterator>& rhs)

---

template <typename TIterator>
ETL_CONSTEXPR14
bool operator ==(const etl::circular_iterator<TIterator>& lhs,
                 const etl::circular_iterator<TIterator>& rhs)

---

template <typename TIterator>
ETL_CONSTEXPR14 bool operator ==(const etl::circular_iterator<TIterator>& lhs,
                                 TIterator rhs)

---

template <typename TIterator>
ETL_CONSTEXPR14 bool operator ==(TIterator lhs,
                                 const etl::circular_iterator<TIterator>& rhs)

---

template <typename TIterator>
ETL_CONSTEXPR14 bool operator !=(const etl::circular_iterator<TIterator>& lhs,
                                 const etl::circular_iterator<TIterator>& rhs)

---

template <typename TIterator>
ETL_CONSTEXPR14 bool operator !=(const etl::circular_iterator<TIterator>& lhs,
                                 TIterator rhs)

---

template <typename TIterator>
ETL_CONSTEXPR14 bool operator !=(TIterator& lhs,
                                 const etl::circular_iterator<TIterator>& rhs)

Example

std::list<int> data{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

// The start position to loop from.
std::list<int>::const_iterator> start = data.begin();
std::advance(start, 2);

// Create circular iterators.
etl::circular_iterator<std::list<int>::const_iterator>> cli(data.begin(), data.end(), start);
etl::circular_iterator<std::list<int>::const_reverse_iterator>> clri(data.rbegin(), data.rend);

// Loop 10 times, taking every third value, starting from the third element for the forward iterator and from the end for the reverse iterator.
for (int = 0; i < 10; ++i)
{
    std::cout << "(" << *cli << "," << *clrl << ")";
    std::advance(cli, 3);
    std::advance(clri, 3);
}

Prints the following
(2,9)(5,6)(8,3)(1,0)(4,7)(7,4)(0,1)(3,8)(6,5)(9,2)