W3cubDocs

/C++

std::shared_ptr<T>::operator==, !=, <, <=, >, >=

Compare two shared_ptr objects
template < class T, class U > 
bool operator==( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ) noexcept;
(1) (since C++11)
template< class T, class U > 
bool operator!=( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ) noexcept;
(2) (since C++11)
template< class T, class U > 
bool operator<( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ) noexcept;
(3) (since C++11)
template< class T, class U > 
bool operator>( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ) noexcept;
(4) (since C++11)
template< class T, class U > 
bool operator<=( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ) noexcept;
(5) (since C++11)
template< class T, class U > 
bool operator>=( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ) noexcept;
(6) (since C++11)
Compare a shared_ptr with a null pointer
template< class T > 
bool operator==( const shared_ptr<T>& lhs, std::nullptr_t rhs ) noexcept;
(7) (since C++11)
template< class T >
bool operator==( std::nullptr_t lhs, const shared_ptr<T>& rhs ) noexcept;
(8) (since C++11)
template< class T >
bool operator!=( const shared_ptr<T>& lhs, std::nullptr_t rhs ) noexcept;
(9) (since C++11)
template< class T >
bool operator!=( std::nullptr_t lhs, const shared_ptr<T>& rhs ) noexcept;
(10) (since C++11)
template< class T >
bool operator<( const shared_ptr<T>& lhs, std::nullptr_t rhs ) noexcept;
(11) (since C++11)
template< class T >
bool operator<( std::nullptr_t lhs, const shared_ptr<T>& rhs ) noexcept;
(12) (since C++11)
template< class T >
bool operator>( const shared_ptr<T>& lhs, std::nullptr_t rhs ) noexcept;
(13) (since C++11)
template< class T >
bool operator>( std::nullptr_t lhs, const shared_ptr<T>& rhs ) noexcept;
(14) (since C++11)
template< class T >
bool operator<=( const shared_ptr<T>& lhs, std::nullptr_t rhs ) noexcept;
(15) (since C++11)
template< class T >
bool operator<=( std::nullptr_t lhs, const shared_ptr<T>& rhs ) noexcept;
(16) (since C++11)
template< class T >
bool operator>=( const shared_ptr<T>& lhs, std::nullptr_t rhs ) noexcept;
(17) (since C++11)
template< class T >
bool operator>=( std::nullptr_t lhs, const shared_ptr<T>& rhs ) noexcept;
(18) (since C++11)

Compares two shared_ptr<T> objects or compares shared_ptr<T> with a null pointer.

Note that the comparison operators for shared_ptr simply compare pointer values; the actual objects pointed to are not compared. Having operator< defined for shared_ptr allows shared_ptrs to be used as keys in associative containers, like std::map and std::set.

Parameters

lhs - the left-hand shared_ptr to compare
rhs - the right-hand shared_ptr to compare

Return value

1) lhs.get() == rhs.get()
2) !(lhs == rhs)
3) std::less<V>()(lhs.get(), rhs.get()), where V is the composite pointer type of std::shared_ptr<T>::element_type* and std::shared_ptr<U>::element_type*
4) rhs < lhs
5) !(rhs < lhs)
6) !(lhs < rhs)
7) !lhs
8) !rhs
9) (bool)lhs
10) (bool)rhs
11) std::less<std::shared_ptr<T>::element_type*>()(lhs.get(), nullptr)
12) std::less<std::shared_ptr<T>::element_type*>()(nullptr, rhs.get())
13) nullptr < lhs
14) rhs < nullptr
15) !(nullptr < lhs)
16) !(rhs < nullptr)
17) !(lhs < nullptr)
18) !(nullptr < rhs)

Notes

In all cases, it is the stored pointer (the one returned by get()) that is compared, rather than the managed pointer (the one passed to the deleter when use_count goes to zero). The two pointers may differ in a shared_ptr created using the aliasing constructor.

Example

See also

returns the stored pointer
(public member function)

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/memory/shared_ptr/operator_cmp