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