std:: less<void>

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Defined in header <functional>
template <>
class less < void > ;
(since C++14)

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

Nested types

Nested type Definition
is_transparent unspecified

Member functions

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

std::less<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>
 
constexpr bool strictly_negative(int lhs)
{
    return std::less<>()(lhs, 0);
}
 
int main()
{
    constexpr signed low = 010;
    constexpr unsigned high = 10;
    std::less<> less{};
    static_assert(less(low, high));
 
    constexpr static auto arr = {0, -1, -2, -3, -4, -5};
    static_assert(!std::all_of(arr.begin(), arr.end(), strictly_negative));
    static_assert(std::all_of(arr.begin() + 1, arr.end(), strictly_negative));
}

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
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