std::owner_less

 

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Defined in header <memory>
template<> struct owner_less<void>;		(since C++17)

std::owner_less<> is a specialization of std::owner_less with parameter types deduced.

Member types

Member type	Definition
is_transparent	/* unspecified */

Notes

The member type is_transparent indicates to the caller that this function object is a transparent function object: it accepts arguments of arbitrary types and uses perfect forwarding, which avoids unnecessary copying and conversion when the function object is used in heterogeneous context, or with rvalue arguments. In particular, template functions such as std::set::find and std::set::lower_bound make use of this member type on their Compare types.

Feature-test macro:

__cpp_lib_transparent_operators

Member functions

operator()

compares its arguments using owner-based semantics (function)

std::owner_less<void>::operator()

template<class T, class U> bool operator()( const std::shared_ptr<T>& lhs,                  const std::shared_ptr<U>& rhs ) const noexcept;		(since C++17)
template<class T, class U> bool operator()( const std::shared_ptr<T>& lhs,                  const std::weak_ptr<U>& rhs ) const noexcept;		(since C++17)
template<class T, class U> bool operator()( const std::weak_ptr<T>& lhs,                  const std::shared_ptr<U>& rhs ) const noexcept;		(since C++17)
template<class T, class U> bool operator()( const std::weak_ptr<T>& lhs,                  const std::weak_ptr<U>& rhs ) const noexcept;		(since C++17)

Compares lhs and rhs using owner-based semantics. Effectively calls lhs.owner_before(rhs).

The ordering is strict weak ordering relation.

lhs and rhs are equivalent only if they are both empty or share ownership.

Parameters

lhs, rhs

-

shared-ownership pointers to compare

Return value

true if lhs is less than rhs as determined by the owner-based ordering.

See also

owner_before	provides owner-based ordering of shared pointers (public member function of std::shared_ptr<T>)
owner_before	provides owner-based ordering of weak pointers (public member function of std::weak_ptr<T>)