operator==,!=,<,<=,>,>=,<=>(std::unique_ptr)
Declaration
- C++23
- C++20
- C++11
// 1)
template< class T1, class D1, class T2, class D2 >
constexpr bool operator==( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 3)
template< class T1, class D1, class T2, class D2 >
bool operator<( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 4)
template< class T1, class D1, class T2, class D2 >
bool operator<=( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y )
// 5)
template< class T1, class D1, class T2, class D2 >
bool operator>( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 6)
template< class T1, class D1, class T2, class D2 >
bool operator>=( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 7)
template< class T1, class D1, class T2, class D2 >
requires std::three_way_comparable_with<
typename unique_ptr<T1, D1>::pointer,
typename unique_ptr<T2, D2>::pointer>
std::compare_three_way_result_t<typename unique_ptr<T1, D1>::pointer,
typename unique_ptr<T2, D2>::pointer>
operator<=>( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 8)
template< class T, class D >
constexpr bool operator==( const unique_ptr<T, D>& x, std::nullptr_t) noexcept;
// 12)
template< class T, class D >
constexpr bool operator<( const unique_ptr<T, D>& x, std::nullptr_t );
// 13)
template< class T, class D >
constexpr bool operator<(std::nullptr_t, const unique_ptr<T, D>& y );
// 14)
template< class T, class D >
constexpr bool operator<=( const unique_ptr<T, D>& x, std::nullptr_t );
// 15)
template< class T, class D >
constexpr bool operator<=(std::nullptr_t, const unique_ptr<T, D>& y );
// 16)
template< class T, class D >
constexpr bool operator>( const unique_ptr<T, D>& x, std::nullptr_t );
// 17)
template< class T, class D >
constexpr bool operator>(std::nullptr_t, const unique_ptr<T, D>& y );
// 18)
template< class T, class D >
constexpr bool operator>=( const unique_ptr<T, D>& x, std::nullptr_t );
// 19)
template< class T, class D >
constexpr bool operator>=(std::nullptr_t, const unique_ptr<T, D>& y );
// 20)
template< class T, class D >
requires std::three_way_comparable<typename unique_ptr<T, D>::pointer>
constexpr std::compare_three_way_result_t<typename unique_ptr<T, D>::pointer>
operator<=>( const unique_ptr<T, D>& x, std::nullptr_t );
// 1)
template< class T1, class D1, class T2, class D2 >
bool operator==( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 3)
template< class T1, class D1, class T2, class D2 >
bool operator<( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 4)
template< class T1, class D1, class T2, class D2 >
bool operator<=( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y )
// 5)
template< class T1, class D1, class T2, class D2 >
bool operator>( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 6)
template< class T1, class D1, class T2, class D2 >
bool operator>=( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 7)
template< class T1, class D1, class T2, class D2 >
requires std::three_way_comparable_with<
typename unique_ptr<T1, D1>::pointer,
typename unique_ptr<T2, D2>::pointer>
std::compare_three_way_result_t<typename unique_ptr<T1, D1>::pointer,
typename unique_ptr<T2, D2>::pointer>
operator<=>( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 8)
template< class T, class D >
bool operator==( const unique_ptr<T, D>& x, std::nullptr_t) noexcept;
// 12)
template< class T, class D >
bool operator<( const unique_ptr<T, D>& x, std::nullptr_t );
// 13)
template< class T, class D >
bool operator<(std::nullptr_t, const unique_ptr<T, D>& y );
// 14)
template< class T, class D >
bool operator<=( const unique_ptr<T, D>& x, std::nullptr_t );
// 15)
template< class T, class D >
bool operator<=(std::nullptr_t, const unique_ptr<T, D>& y );
// 16)
template< class T, class D >
bool operator>( const unique_ptr<T, D>& x, std::nullptr_t );
// 17)
template< class T, class D >
bool operator>(std::nullptr_t, const unique_ptr<T, D>& y );
// 18)
template< class T, class D >
bool operator>=( const unique_ptr<T, D>& x, std::nullptr_t );
// 19)
template< class T, class D >
bool operator>=(std::nullptr_t, const unique_ptr<T, D>& y );
// 20)
template< class T, class D >
requires std::three_way_comparable<typename unique_ptr<T, D>::pointer>
std::compare_three_way_result_t<typename unique_ptr<T, D>::pointer>
operator<=>( const unique_ptr<T, D>& x, std::nullptr_t );
// 1)
template< class T1, class D1, class T2, class D2 >
bool operator==( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 2)
template< class T1, class D1, class T2, class D2 >
bool operator!=( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 3)
template< class T1, class D1, class T2, class D2 >
bool operator<( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 4)
template< class T1, class D1, class T2, class D2 >
bool operator<=( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y )
// 5)
template< class T1, class D1, class T2, class D2 >
bool operator>( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 6)
template< class T1, class D1, class T2, class D2 >
bool operator>=( const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y );
// 8)
template< class T, class D >
bool operator==( const unique_ptr<T, D>& x, std::nullptr_t) noexcept;
// 9)
template< class T, class D >
bool operator==(std::nullptr_t, const unique_ptr<T, D>& x) noexcept;
// 10)
template< class T, class D >
bool operator!=( const unique_ptr<T, D>& x, std::nullptr_t) noexcept;
// 11)
template< class T, class D >
bool operator!=(std::nullptr_t, const unique_ptr<T, D>& x) noexcept;
// 12)
template< class T, class D >
bool operator<( const unique_ptr<T, D>& x, std::nullptr_t );
// 13)
template< class T, class D >
bool operator<(std::nullptr_t, const unique_ptr<T, D>& y );
// 14)
template< class T, class D >
bool operator<=( const unique_ptr<T, D>& x, std::nullptr_t );
// 15)
template< class T, class D >
bool operator<=(std::nullptr_t, const unique_ptr<T, D>& y );
// 16)
template< class T, class D >
bool operator>( const unique_ptr<T, D>& x, std::nullptr_t );
// 17)
template< class T, class D >
bool operator>(std::nullptr_t, const unique_ptr<T, D>& y );
// 18)
template< class T, class D >
bool operator>=( const unique_ptr<T, D>& x, std::nullptr_t );
// 19)
template< class T, class D >
bool operator>=(std::nullptr_t, const unique_ptr<T, D>& y );
Compares the pointer values of two unique_ptr
s, or a unique_ptr
and nullptr
.
1-7)
Compares two unique_ptr
s
8-20)
Compares a unique_ptr
and nullptr
.
The !=
operator is synthesized from operator==
.(since C++20)
Parameters
x
, y
- unique_ptr
s to compare
Return value
x.get() == y.get()
x.get() != y.get()
std::less<CT>()(x.get(), y.get())
,
whereCT
isstd::common_type<unique_ptr<T1, D1>::pointer, unique_ptr<T2, D2>::pointer>::type
!(y < x)
y < x
!(x < y)
std::compare_three_way{}(x.get(), y.get())
8-9)!x
10-11)(bool)x
std::less<unique_ptr<T,D>::pointer>()(x.get(), nullptr)<br/>
std::less<unique_ptr<T,D>::pointer>()(nullptr, y.get())<br/>
!(nullptr < x)
!(y < nullptr)
nullptr < x
y < nullptr
!(x < nullptr)
!(nullptr < y)
std::compare_three_way{}(x.get(), static_cast<typename unique_ptr<T, D>::pointer>(nullptr))
Example
#include <iostream>
#include <memory>
int main()
{
std::unique_ptr<int> p1(new int(42));
std::unique_ptr<int> p2(new int(42));
std::cout << std::boolalpha
<< "(p1 == p1) : "
<< (p1 == p1) << '\n'
<< "(p1 <=> p1) == 0 : "
<< ((p1 <=> p1) == 0) << '\n' // Since C++20
// p1 and p2 point to different memory locations, so p1 != p2
<< "(p1 == p2) : "
<< (p1 == p2) << '\n'
<< "(p1 < p2) : "
<< (p1 < p2) << '\n'
<< "(p1 <=> p2) < 0 : "
<< ((p1 <=> p2) < 0) << '\n' // Since C++20
<< "(p1 <=> p2) == 0 : "
<< ((p1 <=> p2) == 0) << '\n'; // Since C++20
}
Possible Result
(p1 == p1) : true
(p1 <=> p1) == 0 : true
(p1 == p2) : false
(p1 < p2) : true
(p1 <=> p2) < 0 : true
(p1 <=> p2) == 0 : false
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 3426 | C++20 | uoperator<=>(unique_ptr, nullptr_t) was ill-formed | constraints and definition fixed |