(C++) Negater

 

A negater is a type of functor that allows to express the opposite of a predicate [1].

 

Negaters are useful when using algorithms.

 

 

 

 

 

Example (using Boost.Bind)

 

The example below demonstrates how to a find a not-male (that is, a female) using the std::not1 negater.

 

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#include <algorithm> #include <vector> #include <boost/bind.hpp> struct Person {   Person(const bool is_male) : m_is_male(is_male) {}   bool IsMale() const { return m_is_male; }   const bool m_is_male; }; bool HasFemale(const std::vector<const Person *>& v) {   return std::find_if(     v.begin(),v.end(),     std::not1(boost::mem_fn(&Person::IsMale))     ) != v.end(); }

 

 

 

 

 

References

 

1. Bjarne Stroustrup. The C++ Programming Language (3rd edition). ISBN: 0-201-88954-4. Chapter 18.4.4: 'A negater allows us to express the opposite of a predicate'