std::experimental::pmr::polymorphic_allocator<T>::polymorphic_allocator
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                    < cpp | experimental | polymorphic allocator
                    
                                                            
                    |   polymorphic_allocator() noexcept;  | 
(1) | |
|   polymorphic_allocator( const polymorphic_allocator& other ) noexcept = default;  | 
(2) | |
|   template< class U >  polymorphic_allocator( const polymorphic_allocator<U>& other ) noexcept;  | 
(3) | |
|   polymorphic_allocator( memory_resource* r);  | 
(4) | |
Constructs a new polymorphic_allocator.
1) Constructs a 
polymorphic_allocator using the return value of std::experimental::pmr::get_default_resource() as the underlying memory resource.2-3) Constructs a 
polymorphic_allocator using other.resource() as the underlying memory resource.4) Constructs a 
polymorphic_allocator using r as the underlying memory resource. This constructor provides an implicit conversion from memory_resource*.Parameters
| other | - |   another polymorphic_allocator to copy from
 | 
| r | - | pointer to the memory resource to use. May not be null. | 
Exceptions
4) Throws nothing.