C++

Reference

<functional>

class template
<functional>

std::binary_negate

template <class Predicate> class binary_negate;
Negate binary function object class
Binary function object class whose call returns the opposite of another binary function, passed to its constructor.

Object of type binary_negate are generally constructed using function not2.

The class is defined with the same behavior as:

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template <class Predicate> class binary_negate
  : public binary_function <typename Predicate::first_argument_type,
                            typename Predicate::second_argument_type, bool>
{
protected:
  Predicate fn_;
public:
  explicit binary_negate ( const Predicate& pred ) : fn_ (pred) {}
  bool operator() (const typename Predicate::first_argument_type& x,
                   const typename Predicate::second_argument_type& y) const
  { return !fn_(x,y); }
};
 
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template <class Predicate> class binary_negate
{
protected:
  Predicate fn_;
public:
  explicit binary_negate (const Predicate& pred) : fn_ (pred) {}
  bool operator() (const typename Predicate::argument_type& x) const {return !fn_(x,y);}
  typedef typename Predicate::first_argument_type  first_argument_type;
  typedef typename Predicate::second_argument_type second_argument_type;
  typedef bool result_type;
};

Template parameters

Predicate
A binary function object class, with members first_argument_type and second_argument_type defined.

Member types

member typedefinitionnotes
first_argument_typeTType of the first argument in member operator()
second_argument_typeTType of the second argument in member operator()
result_typeTType returned by member operator()

Member functions

constructor
Constructs an object whose functional call returns the opposite as the object passed as its argument.
operator()
Member function returning the opposite of the function object with which the object was constructed.

Example

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// binary_negate example
#include <iostream>     // std::cout
#include <functional>   // std::binary_negate, std::equal_to
#include <algorithm>    // std::mismatch
#include <utility>      // std::pair

int main () {
  std::equal_to<int> equality;
  std::binary_negate < std::equal_to<int> > nonequality (equality);
  int foo[] = {10,20,30,40,50};
  int bar[] = {0,15,30,45,60};
  std::pair<int*,int*> firstmatch,firstmismatch;
  firstmismatch = std::mismatch (foo,foo+5,bar,equality);
  firstmatch = std::mismatch (foo,foo+5,bar,nonequality);
  std::cout << "First mismatch in bar is " << *firstmismatch.second << "\n";
  std::cout << "First match in bar is " << *firstmatch.second << "\n";
  return 0;
}

Output:

First mismatch in bar is 0
First match in bar is 30


See also

not2
Return negation of binary function object (function template)
unary_negate
Negate unary function object class (class template)
binary_function
Binary function object base class (class template)