56 lines
1.8 KiB
Markdown
56 lines
1.8 KiB
Markdown
[polymorphic.swap]
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# 20 Memory management library [[mem]](./#mem)
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## 20.4 Types for composite class design [[mem.composite.types]](mem.composite.types#polymorphic.swap)
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### 20.4.2 Class template polymorphic [[polymorphic]](polymorphic#swap)
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#### 20.4.2.7 Swap [polymorphic.swap]
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[ð](#lib:swap,polymorphic)
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`constexpr void swap(polymorphic& other)
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noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
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allocator_traits<Allocator>::is_always_equal::value);
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7412)
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*Preconditions*: If allocator_traits<Allocator>::propagate_on_container_swap::value is true, thenAllocator meets the *Cpp17Swappable* requirements[.](#1.sentence-1)
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Otherwise get_allocator() == other.
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get_allocator() is true[.](#1.sentence-2)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7419)
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*Effects*: Swaps the states of *this and other,
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exchanging owned objects or valueless states[.](#2.sentence-1)
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If allocator_traits<Allocator>::propagate_on_container_swap::value is true, then
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the allocators of *this and other are exchanged by calling swap as described in [[swappable.requirements]](swappable.requirements "16.4.4.3 Swappable requirements")[.](#2.sentence-2)
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Otherwise,
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the allocators are not swapped[.](#2.sentence-3)
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[*Note [1](#note-1)*:
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Does not call swap on the owned objects directly[.](#2.sentence-4)
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â *end note*]
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[ð](#itemdecl:2)
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`constexpr void swap(polymorphic& lhs, polymorphic& rhs) noexcept(noexcept(lhs.swap(rhs)));
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`
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7442)
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*Effects*: Equivalent to lhs.swap(rhs)[.](#3.sentence-1)
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