std:: less_equal<void>

From cppreference.com
C++
Utilities library
General utilities
Relational operators (deprecated in C++20)
Function objects
Function invocation
(C++17) (C++23)
Identity function object
(C++20)
Old binders and adaptors
( until C++17* )
( until C++17* )
( until C++17* )
( until C++17* )
( until C++17* )
( until C++17* )
( until C++17* ) ( until C++17* ) ( until C++17* ) ( until C++17* )
( until C++20* )
( until C++20* )
( until C++17* ) ( until C++17* )
( until C++17* ) ( until C++17* )

( until C++17* )
( until C++17* ) ( until C++17* ) ( until C++17* ) ( until C++17* )
( until C++20* )
( until C++20* )
Defined in header <functional>
template <>
class less_equal < void > ;
(since C++14)

std:: less_equal < void > is a specialization of std::less_equal with parameter and return type deduced.

Nested types

Nested type Definition
is_transparent unspecified

Member functions

operator()
tests if lhs compares less or equal than rhs
(public member function)

std::less_equal<void>:: operator()

template < class T, class U >

constexpr auto operator ( ) ( T && lhs, U && rhs ) const

- > decltype ( std:: forward < T > ( lhs ) <= std:: forward < U > ( rhs ) ) ;

Returns the result of std:: forward < T > ( lhs ) <= std:: forward < U > ( rhs ) .

Parameters

lhs, rhs - values to compare

Return value

std:: forward < T > ( lhs ) <= std:: forward < U > ( rhs ) .

If a built-in operator comparing pointers is called, the result is consistent with the implementation-defined strict total order over pointers .

Exceptions

May throw implementation-defined exceptions.

Example

Run this code 
#include <algorithm>
#include <functional>
#include <initializer_list>
 
constexpr bool strictly_not_positive(int lhs)
{
    return std::less_equal<>()(lhs, 0);
}
 
int main()
{
    constexpr int low = 0, high = 8;
    std::less_equal<> less_equal{};
    static_assert(less_equal(low, high));
    static_assert(less_equal(low, low));
 
    static constexpr auto arr = {1, 0, -1, -2, -3, -4};
    static_assert(!std::all_of(arr.begin(), arr.end(), strictly_not_positive));
    static_assert(std::all_of(arr.begin() + 1, arr.end(), strictly_not_positive));
}

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 2562 C++98 the pointer total order might be inconsistent guaranteed to be consistent
Retrieved from " https://en.cppreference.com/mwiki/index.php?title=cpp/utility/functional/less_equal_void&oldid=171016 "