array_view

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.

STL equivalent: None at the moment. Similar to the proposed addition to C++17 but restricts the range to a single

dimension.

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>

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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 };

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Member types

value_type T

size_type std::size_t

difference_type std::ptrdiff_t

reference value_type&

const_reference const value_type&

pointer value_type*

const_pointer const value_type*

iterator Random access iterator

const_iterator Constant random access iterator

reverse_iterator std::reverse_iterator<iterator>

const_reverse_iterator std::reverse_iterator<const_iterator>

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Constructors

ETL_CONSTEXPR array_view()

Default constructor.

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template <typename TArray>

ETL_CONSTEXPR explicit array_view(TArray& a)

Construct from array or vector like class.

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template <typename TIterator>

ETL_CONSTEXPR array_view(TIterator begin_, TIterator end_)

Construct from an iterator or pointer range.

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template <typename TIterator, typename TSize>

ETL_CONSTEXPR array_view(TIterator begin_, TSize size_)

Construct from a start and size

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template<const size_t ARRAY_SIZE>

ETL_CONSTEXPR explicit array_view(T(&begin_)[ARRAY_SIZE])

Construct from a compile time sized C array.

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ETL_CONSTEXPR array_view(const array_view& other)

Copy constructor.

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Modifiers

template <typename TIterator>

void assign(TIterator begin_, TIterator end_)

Assigns begin and end of the supplied range.

Does not copy the elements in the range.

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template <typename TIterator, typename TSize>

void assign(TIterator begin_, TSize size_)

Assign from a start iterator and length.

Does not copy the elements in the range.

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void remove_prefix(size_type n)

Shrinks the view from the front.

A value of n larger than the array will result in undefined behaviour.

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void remove_suffix(size_type n)

Shrinks the view from the back.

A value of n larger than the array will result in undefined behaviour.

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void fill(value_type value)

20.24.0

Fill the underlying array with value.

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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

Returns 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.

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reference operator[](size_t i)

const_reference operator[](size_t i) const

Returns a reference or const reference to the indexed element.

Index out of range results in undefined behaviour.

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reference front()

const_reference front() const

Returns a reference or const reference to the first element.

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reference back()

const_reference back() const

Returns a reference or const reference to the last element.

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pointer data()

const_pointer data() const

Returns a pointer or const pointer to the first element.

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Iterators

iterator begin()

const_iterator begin() const

const_iterator cbegin() const

Returns an iterator to the beginning of the array view.

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iterator end()

const_iterator end() const

const_iterator cend() const

Returns an iterator to the end of the array view.

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iterator rbegin()

const_iterator rbegin() const

const_iterator crbegin() const

Returns a reverse iterator to the beginning of the array view.

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iterator rend()

const_iterator rend() const

const_iterator crend() const

Returns a reverse iterator to the end of the array view.

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Capacity

bool empty() const

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

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size_t size() const

Returns the size of the view.

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size_t max_size() const

Returns the maximum possible size of the view.

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Non-member functions

Lexicographically comparisons

== true if the contents of the array views are equal, otherwise false.

!= true if the contents of the array views are not equal, otherwise false.

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

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

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

>= 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

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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);

array_view.h