logical_not


class template
<functional> 
template <class T> struct logical_not;

Logical NOT function object class

This class defines function objects for the "not" logical operation (!).

Generically, function objects are instances of a class with member function operator() defined. This member function allows the object to be used with the same syntax as a regular function call, and therefore it can be used in templates instead of a pointer to a function.

logical_not has its operator() member defined such that it returns true if its argument is false, and false if its argument is true, inverting its value.

This class is derived from unary_function and is defined as:

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template <class T> struct logical_not : unary_function <T,bool> {
  bool operator() (const T& x) const
    {return !x;}
};


Objects of this class can be used with several standard algorithms (see algorithm).

Members

T operator() (const T& x)
Member function returning the result of !x.


Example

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// logical_not example
#include <iostream>
#include <functional>
#include <algorithm>
using namespace std;

int main () {
  bool values[] = {true,false};
  bool result[2];
  transform (values, values+2, result, logical_not<bool>() );
  cout << boolalpha << "Logical NOT:\n";
  for (int i=0; i<2; i++)
	  cout << "NOT " << values[i] << " = " << result[i] << "\n";
  return 0;
}


Output:

Logical NOT:
NOT true = false
NOT false = true


See also

logical_and Logical AND function object class (class template)
logical_or Logical OR function object class (class template)
unary_function Unary function object base class (class template)