etl/docs/containers/Views/array-view.md

title
array_view

{{< callout >}} Header: array_view.h
Since: All versions
Similar to: gsl::array_view {{< /callout >}}

This class implements a view in to a range of a C array, etl::array, std::array, etl::vector and std::vector.
It will support construction from any class that supports data() and size() member functions as well as plain C arrays.

If ETL_ARRAY_VIEW_IS_MUTABLE is defined, then the contents of the view are mutable. The view is non-mutable by default, which is the opposite to the behaviour in 17.5.0 or earlier.

etl::array_view<typename T>

Template deduction guides

C++17 and above

template <typename TArray>
etl::array_view(TArray& a) 
  -> etl::array_view<typename TArray::value_type>;

template <typename TIterator>
etl::array_view(const TIterator begin_, const TIterator end_)
  -> etl::array_view<etl::remove_pointer_t<TIterator>>;

template <typename TIterator, typename TSize>
etl::array_view(const TIterator begin_, const TSize size_)
  -> etl::array_view<etl::remove_pointer_t<TIterator>>;

Examples

etl::array data{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
      
etl::array_view view1{ data };
etl::array_view view2{ data.begin(), data.end() };
etl::array_view view3{ data.begin(), data.size() };
etl::array_view view4{ view1 };

Member types

value_type size_type difference_type reference const_reference pointer const_pointer iterator const_iterator reverse_iterator const_reverse_iterator

Constructors

ETL_CONSTEXPR array_view()

Description
Default constructor.

---

template <typename TArray>
ETL_CONSTEXPR explicit array_view(TArray& a)

Description
Construct from array or vector like class.

---

template <typename TIterator>
ETL_CONSTEXPR array_view(TIterator begin_, TIterator end_)

Description
Construct from an iterator or pointer range.

---

template <typename TIterator, typename TSize>
ETL_CONSTEXPR array_view(TIterator begin_, TSize size_)

Description
Construct from a start and size

---

template<const size_t ARRAY_SIZE>
ETL_CONSTEXPR explicit array_view(T(&begin_)[ARRAY_SIZE])

Description
Construct from a compile time sized C array.

---

ETL_CONSTEXPR array_view(const array_view& other)

Description
Copy constructor.

Modifiers

template <typename TIterator>
void assign(TIterator begin_, TIterator end_)

Description
Assigns begin and end of the supplied range.
Does not copy the elements in the range.

---

template <typename TIterator, typename TSize>
void assign(TIterator begin_, TSize size_)

Description
Assign from a start iterator and length.
Does not copy the elements in the range.

---

void remove_prefix(size_type n)

Description Shrinks the view from the front.
A value of n larger than the array will result in undefined behaviour.

---

void remove_suffix(size_type n)

Description
Shrinks the view from the back.
A value of n larger than the array will result in undefined behaviour.

---

void fill(value_type value)

Introduced: 20.24.0

Description Fill the underlying array with value.

Element access

Mutable access is only possible by defining the macro ETL_ARRAY_VIEW_IS_MUTABLE. In this case, reference, pointer, iterator and reverse_iterator are defined as their const counterparts.

reference at(size_t i)
const_reference at(size_t i) const

Description
Gets a reference or const reference to the indexed element.
Emits an etl::array_view_uninitialised if the view is not initialised.
Emits an etl::array_view_bounds if the index is not in range.
If asserts or exceptions are not enabled then undefined behaviour occurs.

Parameters
i The index.

Returns
A reference or const reference to the indexed element

---

reference operator[](size_t i)
const_reference operator[](size_t i) const

Description
Gets a reference or const reference to the indexed element.

Returns
A reference or const reference to the indexed element.
Undefined behaviour if the array_view is empty.

---

reference front()
const_reference front() const

Description
Gets a reference or const reference to the first element.

Returns
A reference or const reference to the first element.
Undefined behaviour if the array_view is empty.

---

reference back()
const_reference back() const

Description
Gets a reference or const reference to the last element.

Returns
A reference or const reference to the last element.
Undefined behaviour if the array_view is empty.

---

pointer data()
const_pointer data() const

Description
Gets a pointer or const pointer to the first element.

Returns
A pointer or const pointer to the first element.
Equal to end() if the array_view is empty.

Iterators

iterator begin()
const_iterator begin() const
const_iterator cbegin() const

Description
Returns an iterator to the beginning of the array view.

---

iterator end()
const_iterator end() const
const_iterator cend() const

Description
Returns an iterator to the end of the array view.

---

iterator rbegin()
const_iterator rbegin() const
const_iterator crbegin() const

Description
Gets a reverse iterator to the beginning of the array view.

---

iterator rend()
const_iterator rend() const
const_iterator crend() const

Description
Gets a reverse iterator to the end of the array view.

---

Capacity

bool empty() const

Description
Returns true if the size of the array view is zero, otherwise false.

---

size_t size() const

Description
Returns the size of the view.

---

C++size_t max_size() const

Description
Returns the maximum possible size of the view.

---

Non-member functions

Lexicographically comparisons

operator ==

Description
true if the contents of the lists are equal, otherwise false.

---

operator !=

Description
true if the contents of the lists are not equal, otherwise false.

---

operator <

Description
true if the contents of the lhs are lexicographically less than the contents of the rhs, otherwise false.

---

operator <=

Description
true if the contents of the lhs are lexicographically less than or equal to the contents of the rhs, otherwise false.

---

operator >

Description
true if the contents of the lhs are lexicographically greater than the contents of the rhs, otherwise false.

---

operator >=

Description
true if the contents of the lhs are lexicographically greater than or equal to the contents of the rhs, otherwise false.

Hash

There are specialisations of etl::hash for array_view.

Example

etl::array<int, 10> data = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

typedef etl::array_view<int> View;

View view(data.begin() + 2, data.end() - 2);

void Print(const View& view)
{
  for (size_t i = 0; i < view.size(); ++i)
  {
    std::cout << view[i] << " ";
  }
}

Print(view); // Prints "3 4 5 6 7 8"

size_t hashvalue = etl::hash<View>()(view);