logical_not

     Function Object

Unary function object that returns true if its argument is false.

Contents

• Synopsis
• Description
• Interface
• Warning
• See Also

#include <functional>

template <class T>
struct logical_not : unary_function<T, bool> ;

logical_not is a unary function object. Its operator() returns true if its argument is false. You can pass a logical_not object to any algorithm that requires a unary function. For example, the replace_if algorithm replaces an element with another value if the result of a unary operation is true. logical_not is used in that algorithm in the following manner:

vector<int> vec1;

.
.
.
void replace_if(vec1.begin(), vec1.end(),
                logical_not<int>(),1);

This call to replace_if replaces all zeros in the vec1 with "1".

template <class T>

struct logical_not : unary_function<T, bool> {
  typedef typename unary_function<T, bool>::argument_type 
                                            argument_type;
  typedef typename unary_function<T, bool>::result_type result_type;
  bool operator() (const T&) const;
};

If your compiler does not support default template parameters, you will need to always supply the Allocator template arguement. For instance, you will have to write :

vector<int, allocator>

instead of :

vector<int>

Function Objects, unary_function