Difference between revisions of "cpp/named req/Erasable"
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| − | If {{ttb|X}} is not allocator-aware {{rev inl|since=c++23|or is a {{lc|std::basic_string}} specialization}}, the term is defined as if {{ttb|A}} were {{c|std::allocator<T>}}, except that no allocator object needs to be created, and user-defined specializations of {{lc|std::allocator}} are not instantiated. | + | If {{ttb|X}} is not allocator-aware{{rev inl|since=c++23| or is a {{lc|std::basic_string}} specialization}}, the term is defined as if {{ttb|A}} were {{c|std::allocator<T>}}, except that no allocator object needs to be created, and user-defined specializations of {{lc|std::allocator}} are not instantiated. |
===Notes=== | ===Notes=== | ||
Revision as of 18:05, 27 October 2021
Specifies that an object of the type can be destroyed by a given Allocator.
Requirements
The type T is Erasable from the Container X whose value_type is identical to T if, given
A
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an allocator type |
m
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an lvalue of type A
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p
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the pointer of type T* prepared by the container
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where X::allocator_type is identical to std::allocator_traits<A>::rebind_alloc<T>,
the following expression is well-formed:
std::allocator_traits<A>::destroy(m, p);
If X is not allocator-aware or is a std::basic_string specialization(since C++23), the term is defined as if A were std::allocator<T>, except that no allocator object needs to be created, and user-defined specializations of std::allocator are not instantiated.
Notes
All standard library containers require that their element type satisfies Erasable.
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With the default allocator, this requirement is equivalent to the validity of p->~T(), which accepts class types with accessible destructors and all scalar types, but rejects array types, function types, reference types, and void. |
(until C++20) |
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With the default allocator, this requirement is equivalent to the validity of std::destroy_at(p), which accepts class types with accessible destructors and all scalar types, as well as arrays thereof. |
(since C++20) |
See also
| CopyInsertable | |
| MoveInsertable | |
| EmplaceConstructible | |
| Destructible |
