logical_not

Function Object

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• Data Type and Member Function Indexes
• Synopsis
• Description
• Interface
• Warnings
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A unary function object that returns true if its argument is false.

None

#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> {
  bool operator() (const T&) const;
};

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

vector<int, allocator<int> >

instead of:

vector<int>

If your compiler does not support namespaces, then you do not need the using declaration for std.

Function Objects, unary_function