QSpan 类

[constexpr noexcept] bool QSpan:: empty () const

[noexcept] bool QSpan:: isEmpty () const

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.

另请参阅 size () 和 size_bytes ().

[constexpr] QSpan < T > QSpan:: sliced ( QSpan < T , E > ::size_type pos ) const

[constexpr] QSpan < T > QSpan:: subspan ( QSpan < T , E > ::size_type pos ) const

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

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.

另请参阅 subspan (), first (QSpan<T,E>::size_type), and last (QSpan<T,E>::size_type).

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

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

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.

另请参阅 subspan (), first (QSpan<T,E>::size_type), and last (QSpan<T,E>::size_type).

[constexpr] template <typename It, QSpan<T, E>::if_compatible_iterator = true> QSpan:: QSpan ( It first , qsizetype count )

Constructs a QSpan referencing the data starting at first and having length count .

[first, count) must be a valid range.

注意： This constructor participates in overload resolution only if It is a compatible iterator .

[constexpr] template <typename It, QSpan<T, E>::if_compatible_iterator = true> QSpan:: QSpan ( It first , It last )

Constructs a QSpan referencing the data starting at first and having length ( last - first ).

[first, last) must be a valid range.

注意： This constructor participates in overload resolution only if It is a compatible iterator .

[constexpr] template <typename Range, QSpan<T, E>::if_compatible_range = true> QSpan:: QSpan ( Range && r )

Constructs a QSpan referencing the data in the supplied range r .

注意： This constructor participates in overload resolution only if Range is a compatible range .

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

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

注意： This constructor participates in overload resolution only if T is const -qualified.

注意： This constructor is noexcept only if E is std::dynamic_extent .

注意： 若 E 不是 std::dynamic_extent and the size of il 不是 E , the behavior is undefined.

[default] QSpan:: QSpan ()

默认构造函数。

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.

另请参阅 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.

另请参阅 operator[] (), front (), size ()，和 empty ().

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

Returns an interator pointing at the beginning of the span.

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

另请参阅 end (), cbegin (), rbegin (), crbegin ()，和 data ().

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

返回 const_iterator pointing to the beginning of the span.

This will return a read-only iterator even if T 不是 const :

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

另请参阅 cend (), begin (), crbegin (), rbegin ()，和 data ().

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

返回 const_iterator pointing to one past the end of the span.

另请参阅 cbegin (), end (), crend (), rend (), data ()，和 size ().

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

返回 const_reverse_iterator pointing to the beginning of the reversed span.

另请参阅 crend (), rbegin (), cbegin ()，和 begin ().

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

返回 const_reverse_iterator pointing to one past the end of the reversed span.

另请参阅 crbegin (), rend (), cend ()，和 end ().

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

Returns a pointer to the beginning of the span.

The same as calling begin ().

另请参阅 begin () 和 front ().

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

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

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

另请参阅 begin (), cend (), rend (), crend (), data ()，和 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.

注意： This function does not throw any exception when "subspan_always_succeeds_v<Count>" is true.

另请参阅 first (QSpan<T,E>::size_type), last ()，和 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.

另请参阅 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.

另请参阅 operator[] (), back (), size ()，和 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.

注意： This function does not throw any exception when "subspan_always_succeeds_v<Count>" is true.

另请参阅 last (QSpan<T,E>::size_type), first ()，和 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.

另请参阅 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

返回 reverse_iterator pointing to the beginning of the reversed span.

另请参阅 rend (), crbegin (), begin ()，和 cbegin ().

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

返回 reverse_iterator pointing to one past the end of the reversed span.

另请参阅 rbegin (), crend (), end ()，和 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.

另请参阅 size_bytes (), empty ()，和 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) .

另请参阅 size (), empty ()，和 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 偏移 元素。

若 *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 偏移 elements ( E >= 偏移 and size () >= 偏移 ), otherwise the behavior is undefined.

注意： This function does not throw any exception when "subspan_always_succeeds_v<Offset>" is true.

另请参阅 subspan (QSpan<T,E>::size_type), subspan(), first ()，和 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 偏移 .

若 *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.

注意： This function does not throw any exception when "subspan_always_succeeds_v<Offset + Count>" is true.

另请参阅 subspan (QSpan<T,E>::size_type, QSpan<T,E>::size_type), subspan (), first ()，和 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.

另请参阅 front (), back (), size ()，和 empty ().

成员变量文档编制

const std::size_t QSpan:: extent

The second template argument of QSpan<T, E> , that is, E . This is std::dynamic_extent for variable-sized spans.

注意： While all other sizes and indexes in QSpan use qsizetype, this variable, like E , is actually of type size_t , for compatibility with std::span and std::dynamic_extent .

另请参阅 size ().