Annex D (normative) Compatibility features [depr]

D.9 Old adaptable function bindings [depr.func.adaptor.binding]

D.9.3 Negators [depr.negators]

The header <functional> has the following additions:
namespace std {
  template<class Predicate> class unary_negate;
  template<class Predicate>
    constexpr unary_negate<Predicate> not1(const Predicate&);
  template<class Predicate> class binary_negate;
  template<class Predicate>
    constexpr binary_negate<Predicate> not2(const Predicate&);
}
Negators not1 and not2 take a unary and a binary predicate, respectively, and return their logical negations ([expr.unary.op]).
template<class Predicate>
class unary_negate {
public:
  constexpr explicit unary_negate(const Predicate& pred);
  constexpr bool operator()(const typename Predicate::argument_type& x) const;
  using argument_type = typename Predicate::argument_type;
  using result_type   = bool;
};
constexpr bool operator()(const typename Predicate::argument_type& x) const;
Returns: !pred(x).
template<class Predicate> constexpr unary_negate<Predicate> not1(const Predicate& pred);
Returns: unary_­negate<Predicate>(pred).
template<class Predicate>
class binary_negate {
public:
  constexpr explicit binary_negate(const Predicate& pred);
  constexpr bool operator()(const typename Predicate::first_argument_type& x,
                            const typename Predicate::second_argument_type& y) const;
  using first_argument_type  = typename Predicate::first_argument_type;
  using second_argument_type = typename Predicate::second_argument_type;
  using result_type          = bool;

};
constexpr bool operator()(const typename Predicate::first_argument_type& x, const typename Predicate::second_argument_type& y) const;
Returns: !pred(x,y).
template<class Predicate> constexpr binary_negate<Predicate> not2(const Predicate& pred);
Returns: binary_­negate<Predicate>(pred).