[unique.ptr.special]

# 20 Memory management library [[mem]](./#mem)

## 20.3 Smart pointers [[smartptr]](smartptr#unique.ptr.special)

### 20.3.1 Unique-ownership pointers [[unique.ptr]](unique.ptr#special)

#### 20.3.1.6 Specialized algorithms [unique.ptr.special]

[🔗](#lib:swap(unique_ptr&,_unique_ptr&))

`template<class T, class D> constexpr void swap(unique_ptr<T, D>& x, unique_ptr<T, D>& y) noexcept;
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3225)

*Constraints*: is_swappable_v<D> is true[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3229)

*Effects*: Calls x.swap(y)[.](#2.sentence-1)

[🔗](#lib:operator==,unique_ptr)

`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](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3241)

*Returns*: x.get() == y.get()[.](#3.sentence-1)

[🔗](#lib:operator%3c,unique_ptr)

`template<class T1, class D1, class T2, class D2>
  constexpr bool operator<(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3253)

Let CT denotecommon_type_t<typename unique_ptr<T1, D1>::pointer, typename unique_ptr<T2, D2>::pointer>

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3260)

*Mandates*: 

- [(5.1)](#5.1)

unique_ptr<T1, D1>​::​pointer is implicitly convertible to CT and

- [(5.2)](#5.2)

unique_ptr<T2, D2>​::​pointer is implicitly convertible to CT[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3267)

*Preconditions*: The specializationless<CT> is a function object type ([[function.objects]](function.objects "22.10 Function objects")) that
induces a strict weak ordering ([[alg.sorting]](alg.sorting "26.8 Sorting and related operations")) on the pointer values[.](#6.sentence-1)

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3273)

*Returns*: less<CT>()(x.get(), y.get())[.](#7.sentence-1)

[🔗](#lib:operator%3e,unique_ptr)

`template<class T1, class D1, class T2, class D2>
  constexpr bool operator>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
`

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3285)

*Returns*: y < x[.](#8.sentence-1)

[🔗](#lib:operator%3c=,unique_ptr)

`template<class T1, class D1, class T2, class D2>
  constexpr bool operator<=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
`

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3297)

*Returns*: !(y < x)[.](#9.sentence-1)

[🔗](#lib:operator%3e=,unique_ptr)

`template<class T1, class D1, class T2, class D2>
  constexpr bool operator>=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
`

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3309)

*Returns*: !(x < y)[.](#10.sentence-1)

[🔗](#lib:operator%3c=%3e,unique_ptr)

`template<class T1, class D1, class T2, class D2>
  requires [three_way_comparable_with](cmp.concept#concept:three_way_comparable_with "17.12.4 Concept three_­way_­comparable [cmp.concept]")<typename unique_ptr<T1, D1>::pointer,
                                     typename unique_ptr<T2, D2>::pointer>
  constexpr 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);
`

[11](#11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3325)

*Returns*: compare_three_way()(x.get(), y.get())[.](#11.sentence-1)

[🔗](#lib:operator==,unique_ptr_)

`template<class T, class D>
  constexpr bool operator==(const unique_ptr<T, D>& x, nullptr_t) noexcept;
`

[12](#12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3337)

*Returns*: !x[.](#12.sentence-1)

[🔗](#lib:operator%3c,unique_ptr_)

`template<class T, class D>
  constexpr bool operator<(const unique_ptr<T, D>& x, nullptr_t);
template<class T, class D>
  constexpr bool operator<(nullptr_t, const unique_ptr<T, D>& x);
`

[13](#13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3351)

*Preconditions*: The specialization less<unique_ptr<T, D>​::​pointer> is
a function object type ([[function.objects]](function.objects "22.10 Function objects")) that induces a strict weak
ordering ([[alg.sorting]](alg.sorting "26.8 Sorting and related operations")) on the pointer values[.](#13.sentence-1)

[14](#14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3357)

*Returns*: The first function template returnsless<unique_ptr<T, D>::pointer>()(x.get(), nullptr)

The second function template returnsless<unique_ptr<T, D>::pointer>()(nullptr, x.get())

[🔗](#lib:operator%3e,unique_ptr_)

`template<class T, class D>
  constexpr bool operator>(const unique_ptr<T, D>& x, nullptr_t);
template<class T, class D>
  constexpr bool operator>(nullptr_t, const unique_ptr<T, D>& x);
`

[15](#15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3378)

*Returns*: The first function template returns nullptr < x[.](#15.sentence-1)

The second function template returns x < nullptr[.](#15.sentence-2)

[🔗](#lib:operator%3c=,unique_ptr_)

`template<class T, class D>
  constexpr bool operator<=(const unique_ptr<T, D>& x, nullptr_t);
template<class T, class D>
  constexpr bool operator<=(nullptr_t, const unique_ptr<T, D>& x);
`

[16](#16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3393)

*Returns*: The first function template returns !(nullptr < x)[.](#16.sentence-1)

The second function template returns !(x < nullptr)[.](#16.sentence-2)

[🔗](#lib:operator%3e=,unique_ptr_)

`template<class T, class D>
  constexpr bool operator>=(const unique_ptr<T, D>& x, nullptr_t);
template<class T, class D>
  constexpr bool operator>=(nullptr_t, const unique_ptr<T, D>& x);
`

[17](#17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3408)

*Returns*: The first function template returns !(x < nullptr)[.](#17.sentence-1)

The second function template returns !(nullptr < x)[.](#17.sentence-2)

[🔗](#lib:operator%3c=%3e,unique_ptr_)

`template<class T, class D>
  requires [three_way_comparable](cmp.concept#concept:three_way_comparable "17.12.4 Concept three_­way_­comparable [cmp.concept]")<typename unique_ptr<T, D>::pointer>
  constexpr compare_three_way_result_t<typename unique_ptr<T, D>::pointer>
    operator<=>(const unique_ptr<T, D>& x, nullptr_t);
`

[18](#18)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L3423)

*Returns*: compare_three_way()(x.get(), static_cast<typename unique_ptr<T, D>::pointer>(nullptr)).