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C++ named requirements: CopyInsertable

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(C++11)
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Specifies that an instance of the type can be copy-constructed in-place by a given allocator.

[edit] Requirements

The type T is CopyInsertable into the container X whose value_type is identical to T if T is MoveInsertable into X, and, given

A an allocator type
m an lvalue of type A
p the pointer of type T* prepared by the container
v expression of type (possibly const) T

where X::allocator_type is identical to std::allocator_traits<A>::rebind_alloc<T>,

the following expression is well-formed:

std::allocator_traits<A>::construct(m, p, v);

And after evaluation, the value of *p is equivalent to the value of v. The value of v is unchanged.

If X is not allocator-aware or is a std::basic_string specialization, 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.

[edit] Notes

If A is std::allocator<T>, then this will call placement-new, as by ::new((void*)p) T(v) (until C++20)std::construct_at(p, v) (since C++20).

Although it is required that customized construct is used when constructing elements of std::basic_string until C++23, all implementations only used the default mechanism. The requirement is corrected by P1072R10 to match existing practice.