cppdraft_translate/cppdraft/span/sub.md

[span.sub]

23 Containers library [containers]

23.7 Views [views]

23.7.2 Contiguous access [views.contiguous]

23.7.2.2 Class template span [views.span]

23.7.2.2.4 Subviews [span.sub]

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template<size_t Count> constexpr span<element_type, Count> first() const;

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Mandates: Count <= Extent is true.

2

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Hardened preconditions: Count <= size() is true.

3

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Effects: Equivalent to: return R{data(), Count}; where R is the return type.

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template<size_t Count> constexpr span<element_type, Count> last() const;

4

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Mandates: Count <= Extent is true.

5

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Hardened preconditions: Count <= size() is true.

6

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Effects: Equivalent to: return R{data() + (size() - Count), Count}; where R is the return type.

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template<size_t Offset, size_t Count = dynamic_extent> constexpr span<element_type, see below> subspan() const;

7

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Mandates: Offset <= Extent && (Count == dynamic_extent || Count <= Extent - Offset) is true.

8

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Hardened preconditions: Offset <= size() && (Count == dynamic_extent || Count <= size() - Offset) is true.

9

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Effects: Equivalent to:return span<ElementType, see below>( data() + Offset, Count != dynamic_extent ? Count : size() - Offset);

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Remarks: The second template argument of the returned span type is:Count != dynamic_extent ? Count : (Extent != dynamic_extent ? Extent - Offset : dynamic_extent)

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constexpr span<element_type, dynamic_extent> first(size_type count) const;

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Hardened preconditions: count <= size() is true.

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Effects: Equivalent to: return {data(), count};

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constexpr span<element_type, dynamic_extent> last(size_type count) const;

13

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Hardened preconditions: count <= size() is true.

14

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Effects: Equivalent to: return {data() + (size() - count), count};

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constexpr span<element_type, dynamic_extent> subspan( size_type offset, size_type count = dynamic_extent) const;

15

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Hardened preconditions: offset <= size() && (count == dynamic_extent || count <= size() - offset) is true.

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Effects: Equivalent to:return {data() + offset, count == dynamic_extent ? size() - offset : count};