Annex D (normative) Compatibility features [depr]

D.8 Old adaptable function bindings [depr.func.adaptor.binding]

D.8.3 Negators [depr.negators]

1
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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&);
}
2
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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;

3
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Returns: !pred(x).

template <class Predicate> constexpr unary_negate<Predicate> not1(const Predicate& pred);

4
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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;

5
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Returns: !pred(x,y).

template <class Predicate> constexpr binary_negate<Predicate> not2(const Predicate& pred);

6
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Returns: binary_­negate<Predicate>(pred).