| Compare two shared_ptr objects | ||
template < class T, class U > bool operator==( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ); | (1) | (since C++11) |
template< class T, class U > bool operator!=( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ); | (2) | (since C++11) |
template< class T, class U > bool operator<( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ); | (3) | (since C++11) |
template< class T, class U > bool operator>( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ); | (4) | (since C++11) |
template< class T, class U > bool operator<=( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ); | (5) | (since C++11) |
template< class T, class U > bool operator>=( const shared_ptr<T>& lhs, const shared_ptr<U>& rhs ); | (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 ); | (7) | (since C++11) |
template< class T > bool operator==( std::nullptr_t lhs, const shared_ptr<T>& rhs ); | (8) | (since C++11) |
template< class T > bool operator!=( const shared_ptr<T>& lhs, std::nullptr_t rhs ); | (9) | (since C++11) |
template< class T > bool operator!=( std::nullptr_t lhs, const shared_ptr<T>& rhs ); | (10) | (since C++11) |
template< class T > bool operator<( const shared_ptr<T>& lhs, std::nullptr_t rhs ); | (11) | (since C++11) |
template< class T > bool operator<( std::nullptr_t lhs, const shared_ptr<T>& rhs ); | (12) | (since C++11) |
template< class T > bool operator>( const shared_ptr<T>& lhs, std::nullptr_t rhs ); | (13) | (since C++11) |
template< class T > bool operator>( std::nullptr_t lhs, const shared_ptr<T>& rhs ); | (14) | (since C++11) |
template< class T > bool operator<=( const shared_ptr<T>& lhs, std::nullptr_t rhs ); | (15) | (since C++11) |
template< class T > bool operator<=( std::nullptr_t lhs, const shared_ptr<T>& rhs ); | (16) | (since C++11) |
template< class T > bool operator>=( const shared_ptr<T>& lhs, std::nullptr_t rhs ); | (17) | (since C++11) |
template< class T > bool operator>=( std::nullptr_t lhs, const shared_ptr<T>& rhs ); | (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 T* and U* 4)
rhs < lhs 5)
!(rhs < lhs) 6)
!(lhs < rhs) 7)
!lhs 8)
!rhs 9)
(bool)lhs 10)
(bool)rhs 11)
std::less<T*>()(lhs.get(), nullptr) 12)
std::less<T*>()(nullptr, rhs.get()) 13)
nullptr < lhs 14)
rhs < nullptr 15)
!(nullptr < lhs) 16)
!(rhs < nullptr) 17)
!(lhs < nullptr) 18)
!(nullptr < rhs) Exceptions
noexcept specification: noexceptNotes
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 a pointer to the managed object (public member function) |
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