std::partial_order

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Utilities library

Language support

Type support (basic types, RTTI)

Library feature-test macros(C++20)

Program utilities

Variadic functions

initializer_list

(C++11)

is_constant_evaluated

(C++20)

is_within_lifetime

(C++26)

source_location

(C++20)

Coroutine support(C++20)

Contract support(C++26)

Three-way comparison

three_way_comparablethree_way_comparable_with

(C++20)(C++20)

strong_ordering

(C++20)

weak_ordering

(C++20)

partial_ordering

(C++20)

common_comparison_category

(C++20)

compare_three_way_result

(C++20)

compare_three_way

(C++20)

strong_order

(C++20)

weak_order

(C++20)

partial_order

(C++20)

compare_strong_order_fallback

(C++20)

compare_weak_order_fallback

(C++20)

compare_partial_order_fallback

(C++20)

is_eqis_ltis_lteq

(C++20)(C++20)(C++20)

is_neqis_gtis_gteq

(C++20)(C++20)(C++20)

General utilities

Function objects
Bit manipulation(C++20)
C-style bit manipulation(C++26)
bitset
hash (C++11)

Relational operators(deprecated in C++20)

rel_ops::operator!=rel_ops::operator>

rel_ops::operator<=rel_ops::operator>=

Integer comparison functions

cmp_equalcmp_lesscmp_less_than

(C++20)(C++20)(C++20)

cmp_not_equalcmp_greatercmp_greater_than

(C++20)(C++20)(C++20)

in_range

(C++20)

Swap andtype operations

swap
ranges::swap (C++20)
exchange (C++14)
declval (C++11)
to_underlying (C++23)

forward (C++11)
forward_like (C++23)
move (C++11)
move_if_noexcept (C++11)
as_const (C++17)

Common vocabulary types

pair
tuple (C++11)
optional (C++17)
any (C++17)
variant (C++17)

tuple_size (C++11)
tuple_element (C++11)
apply (C++17)
make_from_tuple (C++17)
expected (C++23)

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Defined in header`<compare>`
inlinenamespace/* unspecified /{ inlineconstexpr/ unspecified / partial_order=/ unspecified */; }		(since C++20)
Call signature
template<class T,class U> requires/* see below / constexprstd::partial_ordering partial_order( T&& t, U&& u)noexcept(/ see below */);

Compares two values using 3-way comparison and produces a result of typestd::partial_ordering.

Lett andu be expressions andT andU denotedecltype((t)) anddecltype((u)) respectively,std::partial_order(t, u) isexpression-equivalent to:

Ifstd::is_same_v<std::decay_t<T>,std::decay_t<U>> istrue:
- std::partial_ordering(partial_order(t, u)), if it is a well-formed expression with overload resolution performed in a context that does not include a declaration ofstd::partial_order,
- otherwise,std::partial_ordering(std::compare_three_way()(t, u)), if it is well-formed,
- otherwise,std::partial_ordering(std::weak_order(t, u)), if it is well-formed.
In all other cases, the expression is ill-formed, which can result insubstitution failure when it appears in the immediate context of a template instantiation.

Customization point objects

The namestd::partial_order denotes acustomization point object, which is a constfunction object of aliteral semiregular class type. SeeCustomizationPointObject for details.

[edit]Example

This section is incomplete
Reason: no example

[edit]See also

partial_ordering (C++20)	the result type of 3-way comparison that supports all 6 operators, is not substitutable, and allows incomparable values (class)[edit]
strong_order (C++20)	performs 3-way comparison and produces a result of type`std::strong_ordering` (customization point object)[edit]
weak_order (C++20)	performs 3-way comparison and produces a result of type`std::weak_ordering` (customization point object)[edit]
compare_partial_order_fallback (C++20)	performs 3-way comparison and produces a result of type`std::partial_ordering`, even ifoperator<=> is unavailable (customization point object)[edit]