QSpan Class

 int numbers[] = {0, 1, 2};
 QSpan<int> span = numbers;
 span[0] = 42;
 // numbers == {42, 1, 2};
 QSpan<const int> cspan = numbers;
 cspan[0] = 0; // ERROR: cspan[0] is read-only

 int numbers[] = {0, 1, 2};
 QSpan<int, 3> span = numbers;
 QSpan<const int, 3> = numbers; // also OK

 int numbers[] = {0, 1, 2};
 const QSpan<int> span = numbers;
 span.front() = 42;   // OK, numbers[0] == 42 now
 *span.begin() = 31;  // OK, numbers[0] == 31 now
 *span.cbegin() = -1; // ERROR: cannot assign through a const_iterator

 void consume(QSpan<const int> data); // OK
 void consume(const QSpan<const int> &data); // works, but is non-idiomatic and less efficient

Member Function Documentation

These Special Member Functions are implicitly-defined.

[constexpr noexcept] template <size_t N> QSpan::QSpan(q20::type_identity_t<T> (&)[N] arr)

Constructs a QSpan referencing the data in the supplied array arr.

• either N or extent are std::dynamic_extent or otherwise extent == N
• and either S or const S are the same as T.

Returns whether the span is empty, that is, whether size() == 0.

These functions do the same thing: empty() is provided for STL compatibility and isEmpty() is provided for Qt compatibility.

See also size() and size_bytes().

Returns a variable-sized span of size size() - pos referencing the remainder of this span after dropping the first pos elements.

pos must be non-negative.

This span must hold at least pos elements (E >= pos and size() >= pos), otherwise the behavior is undefined.

These functions do the same thing: subspan() is provided for STL compatibility and sliced() is provided for Qt compatibility.

See also subspan(), first(QSpan<T,E>::size_type), and last(QSpan<T,E>::size_type).

Returns a variable-sized span of size n referencing the n elements of this span starting at pos.

Both pos and n must be non-negative.

This span must hold at least pos + n elements (E >= pos + n and size() >= pos + n), otherwise the behavior is undefined.

These functions do the same thing: subspan() is provided for STL compatibility and sliced() is provided for Qt compatibility.

See also subspan(), first(QSpan<T,E>::size_type), and last(QSpan<T,E>::size_type).

[constexpr] QSpan::QSpan(std::initializer_list<QSpan<T, E>::value_type> il)

Constructs a QSpan referencing the data in the supplied initializer list il.

[default] QSpan::QSpan()

Default constructor.

This constructor is only present if E is either zero (0) or std::dynamic_extent. In other words: only fixed-zero-sized or variable-sized spans are default-constructible.

See also extent.

[constexpr] QSpan<T, E>::reference QSpan::back() const

Returns a reference to the last element in the span.

The span must not be empty, otherwise the behavior is undefined.

See also operator[](), front(), size(), and empty().

[constexpr noexcept] QSpan<T, E>::iterator QSpan::begin() const

Returns an interator pointing at the beginning of the span.

Because QSpan iterators are just pointers, this is the same as calling data().

See also end(), cbegin(), rbegin(), crbegin(), and data().

[constexpr noexcept] QSpan<T, E>::const_iterator QSpan::cbegin() const

Returns a const_iterator pointing to the beginning of the span.

This will return a read-only iterator even if T is not const:

 QSpan<int> span = ~~~;
 *span.begin() = 42; // OK
 *span.cbegin() = 42; // ERROR: cannot assign through a const_iterator

See also cend(), begin(), crbegin(), rbegin(), and data().

[constexpr noexcept] QSpan<T, E>::const_iterator QSpan::cend() const

Returns a const_iterator pointing to one past the end of the span.

See also cbegin(), end(), crend(), rend(), data(), and size().

[constexpr noexcept] QSpan<T, E>::const_reverse_iterator QSpan::crbegin() const

Returns a const_reverse_iterator pointing to the beginning of the reversed span.

See also crend(), rbegin(), cbegin(), and begin().

[constexpr noexcept] QSpan<T, E>::const_reverse_iterator QSpan::crend() const

Returns a const_reverse_iterator pointing to one past the end of the reversed span.

See also crbegin(), rend(), cend(), and end().

[constexpr noexcept] QSpan<T, E>::pointer QSpan::data() const

Returns a pointer to the beginning of the span.

The same as calling begin().

See also begin() and front().

[constexpr noexcept] QSpan<T, E>::iterator QSpan::end() const

Returns an iterator pointing to one past the end of the span.

Because QSpan iterators are just pointers, this it the same as calling data() + size().

See also begin(), cend(), rend(), crend(), data(), and size().

[constexpr noexcept(...)] template <std::size_t Count> QSpan<T, Count> QSpan::first() const

Returns a fixed-sized span of size Count referencing the first Count elements of *this.

The span must hold at least Count elements (E >= Count and size() >= Count), otherwise the behavior is undefined.

See also first(QSpan<T,E>::size_type), last(), and subspan().

[constexpr] QSpan<T> QSpan::first(QSpan<T, E>::size_type n) const

Returns a variable-sized span of size n referencing the first n elements of *this.

n must be non-negative.

The span must hold at least n elements (E >= n and size() >= n), otherwise the behavior is undefined.

See also first<N>(), last(QSpan<T,E>::size_type), subspan(QSpan<T,E>::size_type), subspan(QSpan<T,E>::size_type, QSpan<T,E>::size_type), and sliced().

[constexpr] QSpan<T, E>::reference QSpan::front() const

Returns a reference to the first element in the span.

The span must not be empty, otherwise the behavior is undefined.

See also operator[](), back(), size(), and empty().

[constexpr noexcept(...)] template <std::size_t Count> QSpan<T, Count> QSpan::last() const

Returns a fixed-sized span of size Count referencing the last Count elements of *this.

The span must hold at least Count elements (E >= Count and size() >= Count), otherwise the behavior is undefined.

See also last(QSpan<T,E>::size_type), first(), and subspan().

[constexpr] QSpan<T> QSpan::last(QSpan<T, E>::size_type n) const

Returns a variable-sized span of size n referencing the last n elements of *this.

n must be non-negative.

The span must hold at least n elements (E >= n and size() >= n), otherwise the behavior is undefined.

See also last(), first(QSpan<T,E>::size_type), subspan(QSpan<T,E>::size_type), subspan(QSpan<T,E>::size_type, QSpan<T,E>::size_type), and sliced().

[constexpr noexcept] QSpan<T, E>::reverse_iterator QSpan::rbegin() const

Returns a reverse_iterator pointing to the beginning of the reversed span.

See also rend(), crbegin(), begin(), and cbegin().

[constexpr noexcept] QSpan<T, E>::reverse_iterator QSpan::rend() const

Returns a reverse_iterator pointing to one past the end of the reversed span.

See also rbegin(), crend(), end(), and cend().

[constexpr noexcept] QSpan<T, E>::size_type QSpan::size() const

Returns the size of the span, that is, the number of elements it references.

See also size_bytes(), empty(), and isEmpty().

[constexpr noexcept] QSpan<T, E>::size_type QSpan::size_bytes() const

Returns the size of the span in bytes, that is, the number of elements multiplied by sizeof(T).

See also size(), empty(), and isEmpty().

[constexpr noexcept(...)] template <std::size_t Offset> auto QSpan::subspan() const

Returns a span of size E - Offset referencing the remainder of this span after dropping the first Offset elements.

If *this is a variable-sized span, the return type is a variable-sized span, otherwise it is a fixed-sized span.

This span must hold at least Offset elements (E >= Offset and size() >= Offset), otherwise the behavior is undefined.

See also subspan(QSpan<T,E>::size_type), subspan(), first(), and last().

[constexpr noexcept(...)] template <std::size_t Offset, std::size_t Count> auto QSpan::subspan() const

Returns a span of size Count referencing the Count elements of this span starting at Offset.

If *this is a variable-sized span, the return type is a variable-sized span, otherwise it is a fixed-sized span.

This span must hold at least Offset + Count elements (E >= Offset + Count and size() >= Offset + Count), otherwise the behavior is undefined.

See also subspan(QSpan<T,E>::size_type, QSpan<T,E>::size_type), subspan(), first(), and last().

[constexpr] QSpan<T, E>::reference QSpan::operator[](QSpan<T, E>::size_type idx) const

Returns a reference to the element at index idx in the span.

The index must be in range, that is, idx >= 0 and idx < size(), otherwise the behavior is undefined.

See also front(), back(), size(), and empty().