|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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 integerst andu. Unlike builtin comparison operators, negative signed integers always compareless than (andnot equal to) unsigned integers: the comparison is safe against non-value-preserving integer conversion.
-1> 0u;// truestd::cmp_greater(-1, 0u);// false
It is a compile-time error if eitherT orU is a non-integer type, a character type, orbool.
Contents |
| t | - | left-hand argument |
| u | - | right-hand argument |
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);} |
These functions cannot be used to compareenums (includingstd::byte),char,char8_t,char16_t,char32_t,wchar_t andbool.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_integer_comparison_functions | 202002L | (C++20) | Integer comparison functions |
The example below might producedifferent signedness comparison warning if compiled without an appropriate warning suppression flag, e.g.,-Wno-sign-compare (gcc/clang with-Wall -Wextra, see alsoSO: disabling a specific warning).
#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));}
| function object implementingx== y (class template)[edit] | |
| function object implementingx!= y (class template)[edit] | |
| function object implementingx< y (class template)[edit] | |
| function object implementingx> y (class template)[edit] | |
| function object implementingx<= y (class template)[edit] | |
| function object implementingx>= y (class template)[edit] | |
(C++20) | constrained function object implementingx== y (class)[edit] |
(C++20) | constrained function object implementingx!= y (class)[edit] |
(C++20) | constrained function object implementingx< y (class)[edit] |
(C++20) | constrained function object implementingx> y (class)[edit] |
(C++20) | constrained function object implementingx<= y (class)[edit] |
(C++20) | constrained function object implementingx>= y (class)[edit] |
(C++20) | constrained function object implementingx<=> y (class)[edit] |
(C++20) | checks if an integer value is in the range of a given integer type (function template)[edit] |
| provides an interface to query properties of all fundamental numeric types (class template)[edit] |
