std::less<void>

 

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Operator wrappers plus minus negate multiplies divides modulus bit_and bit_or bit_not (C++14)   bit_xor equal_to not_equal_to greater less greater_equal less_equal logical_and logical_or logical_not	Transparent operator wrappers plus<> (C++14) minus<> (C++14) negate<> (C++14) multiplies<> (C++14)   divides<> (C++14) modulus<> (C++14) bit_and<> (C++14) bit_or<> (C++14) bit_not<> (C++14) bit_xor<> (C++14) equal_to<> (C++14) not_equal_to<> (C++14) greater<> (C++14) less<> (C++14) greater_equal<> (C++14) less_equal<> (C++14) logical_and<> (C++14) logical_or<> (C++14) logical_not<> (C++14)
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unary_function (until C++17*) binary_function (until C++17*) ptr_fun (until C++17*) pointer_to_unary_function (until C++17*) pointer_to_binary_function (until C++17*)   mem_fun (until C++17*) mem_fun_tmem_fun1_tconst_mem_fun_tconst_mem_fun1_t (until C++17*)(until C++17*)(until C++17*)(until C++17*) not1 (until C++20*) not2 (until C++20*)	binder1stbinder2nd (until C++17*)(until C++17*) bind1stbind2nd (until C++17*)(until C++17*) mem_fun_ref (until C++17*) mem_fun_ref_tmem_fun1_ref_tconst_mem_fun_ref_tconst_mem_fun1_ref_t (until C++17*)(until C++17*)(until C++17*)(until C++17*) unary_negate (until C++20*) binary_negate (until C++20*)

 

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 > constexprauto 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>   constexprbool strictly_negative(int lhs){returnstd::less<>()(lhs, 0);}   int main(){constexprsigned low =010;constexprunsigned high =10;std::less<> less{}; static_assert(less(low, high));   constexprstaticauto 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