C++ named requirements: MoveInsertable (since C++11)

< cpp‎ | named req
C++ named requirements

Specifies that an object of the type can be constructed into uninitialized storage from an rvalue of that type by a given allocator.

[edit] Requirements

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

A an allocator type
m an lvalue of type A
p the pointer of type T* prepared by the container
rv rvalue expression of type 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, rv);

And after evaluation, the value of *p is equivalent to the value formerly held by rv (rv remains valid, but is in an unspecified state.)

If X is not allocator-aware, 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(rv). This effectively requires T to be move constructible.

If std::allocator<T> or a similar allocator is used, a class does not have to implement a move constructor to satisfy this type requirement: a copy constructor that takes a const T& argument can bind rvalue expressions. If a MoveInsertable class implements a move constructor, it may also implement move semantics to take advantage of the fact that the value of rv after construction is unspecified.

[edit] See Also