STL - inverter

1. Inverter The role of ： To the existing Function object Logic reverses

 

not1  to One yuan Function object Take the opposite

not2  to binary Function object Take the opposite

Let's learn more about the negator through a piece of code

#include <iostream>
#include <functional>
#include <algorithm>
#include <vector>
using namespace std;

int main()
{
	int arr[] = {12,34,42,52,64,62,90,102,46,256,78};
	int len = sizeof(arr) / sizeof(arr[0]);
	vector<int> vec(arr,arr+len);
	
        // Use the binders provided by the system  bind2nd  and   Inverter  not1 
        vector<int>::iterator it1 = find_if(vec.begin(),vec.end(),bind2nd(greater<int>(),100));

        if(it1 != vec.end())
	{
	    cout << " first   Greater than  100 The elements of :" << *it1 << endl;
	}

        vector<int>::iterator it2 = find_if(vec.begin(),vec.end(),not1(bind2nd(greater<int>(),100)));

	if(it2 != vec.end())
	{
	    cout << " first   No   Greater than  100 The elements of :" << *it2 << endl;
	}
		
	return 0;
}

Inverter : not1   The implementation is to negate the internal unary function object of the binder , Like before Greater than   , Now it is Less than or equal to  , That is, not more than

2. Inverter The concrete realization of ：

#include <iostream>
#include <functional>
#include <algorithm>
#include <vector>
using namespace std;

template<typename Fn>
class MyNote
{
public:
    MyNote(Fn & f) :fn(f){}

    bool operator()(const typename Fn::argument_type& val)// Unary function object argument_type
    {
	return !fn(val);
    }
private:
    Fn fn;
};

template<typename Fn>
MyNote<Fn> mynote(Fn f)
{
    return MyNote<Fn>(f);
}

int main()
{
    int arr[] = {12,34,42,52,64,62,90,102,46,256,78};
    int len = sizeof(arr) / sizeof(arr[0]);
    vector<int> vec(arr,arr+len);
	
    vector<int>::iterator it = find_if(vec.begin(),vec.end(),mynote(bind2nd(greater<int>(),100)));

    if(it != vec.end())
    {
	cout << " first   No   Greater than 100 The elements of :" << *it << endl;
    }

    return 0;
}

  summary ： The reverser can be seen as a supplement to the binder