std::cmp_equal, cmp_not_equal, cmp_less, cmp_greater, cmp_less_equal, cmp_greater_equal

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

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) 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 and type 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)

 

Defined in header <utility>
template<class T, class U > constexprbool cmp_equal( T t, U u )noexcept;	(1)	(since C++20)
template<class T, class U > constexprbool cmp_not_equal( T t, U u )noexcept;	(2)	(since C++20)
template<class T, class U > constexprbool cmp_less( T t, U u )noexcept;	(3)	(since C++20)
template<class T, class U > constexprbool cmp_greater( T t, U u )noexcept;	(4)	(since C++20)
template<class T, class U > constexprbool cmp_less_equal( T t, U u )noexcept;	(5)	(since C++20)
template<class T, class U > constexprbool cmp_greater_equal( T t, U u )noexcept;	(6)	(since C++20)

Compare the values of two integers t and u. Unlike builtin comparison operators, negative signed integers always compare less than (and not equal to) unsigned integers: the comparison is safe against non-value-preserving integer conversion.

-1> 0u;// true std::cmp_greater(-1, 0u);// false

It is a compile-time error if either T or U is a non-integer type, a character type, or bool.

Parameters

t	-	left-hand argument
u	-	right-hand argument

Return value

1)true if t is equal to u.

2)true if t is not equal to u.

3)true if t is less than u.

4)true if t is greater than u.

5)true if t is less or equal to u.

6)true if t is greater or equal to u.

Possible implementation

template<class T, class U>constexprbool cmp_equal(T t, U u)noexcept{ifconstexpr(std::is_signed_v<T>==std::is_signed_v<U>)return t == u;elseifconstexpr(std::is_signed_v<T>)return t >=0&&std::make_unsigned_t<T>(t)== u;elsereturn u >=0&&std::make_unsigned_t<U>(u)== t;}   template<class T, class U>constexprbool cmp_not_equal(T t, U u)noexcept{return!cmp_equal(t, u);}   template<class T, class U>constexprbool cmp_less(T t, U u)noexcept{ifconstexpr(std::is_signed_v<T>==std::is_signed_v<U>)return t < u;elseifconstexpr(std::is_signed_v<T>)return t <0||std::make_unsigned_t<T>(t)< u;elsereturn u >=0&& t <std::make_unsigned_t<U>(u);}   template<class T, class U>constexprbool cmp_greater(T t, U u)noexcept{return cmp_less(u, t);}   template<class T, class U>constexprbool cmp_less_equal(T t, U u)noexcept{return!cmp_less(u, t);}   template<class T, class U>constexprbool cmp_greater_equal(T t, U u)noexcept{return!cmp_less(t, u);}

Notes

These functions cannot be used to compare enums (including std::byte), char, char8_t, char16_t, char32_t, wchar_t and bool.

Feature-test macro	Value	Std	Feature
__cpp_lib_integer_comparison_functions	202002L	(C++20)	Integer comparison functions

Example

The example below might produce different signedness comparison warning if compiled without an appropriate warning suppression flag, e.g., -Wno-sign-compare (gcc/clang with -Wall -Wextra, see also SO: disabling a specific warning).

Run this code

#include <utility>   // Uncommenting the next line will disable "signed/unsigned comparison" warnings:// #pragma GCC diagnostic ignored "-Wsign-compare"   int main(){ static_assert(sizeof(int)==4);// precondition   // Quite surprisingly static_assert(-1> 1U);//< warning: sign-unsign comparison// because after implicit conversion of -1 to the RHS type (`unsigned int`)// the expression is equivalent to: static_assert(0xFFFFFFFFU > 1U); static_assert(0xFFFFFFFFU ==static_cast<unsigned>(-1));   // In contrast, the cmp_* family compares integers as most expected -// negative signed integers always compare less than unsigned integers: static_assert(std::cmp_less(-1, 1U)); static_assert(std::cmp_less_equal(-1, 1U)); static_assert(!std::cmp_greater(-1, 1U)); static_assert(!std::cmp_greater_equal(-1, 1U));   static_assert(-1== 0xFFFFFFFFU);//< warning: sign-unsign comparison static_assert(std::cmp_not_equal(-1, 0xFFFFFFFFU));}

See also

equal_to	function object implementing x == y (class template)
not_equal_to	function object implementing x != y (class template)
less	function object implementing x < y (class template)
greater	function object implementing x > y (class template)
less_equal	function object implementing x <= y (class template)
greater_equal	function object implementing x >= y (class template)
ranges::equal_to (C++20)	constrained function object implementing x == y (class)
ranges::not_equal_to (C++20)	constrained function object implementing x != y (class)
ranges::less (C++20)	constrained function object implementing x < y (class)
ranges::greater (C++20)	constrained function object implementing x > y (class)
ranges::less_equal (C++20)	constrained function object implementing x <= y (class)
ranges::greater_equal (C++20)	constrained function object implementing x >= y (class)
compare_three_way (C++20)	constrained function object implementing x <=> y (class)
in_range (C++20)	checks if an integer value is in the range of a given integer type (function template)
numeric_limits	provides an interface to query properties of all fundamental numeric types (class template)