C++11 包装器

#include

template
T useF(F f, T x)
{
	static int count = 0;
	cout << "count:" << ++count << endl;
	cout << "count:" << &count << endl;
	return f(x);
}
double f(double i)
{
	return i / 2;
}
struct Funtor
{
	double operator()(double d)
	{
		return d / 3;
	}
};
int main()
{
	cout << useF(f, 11.11) << endl;
	cout << useF(Funtor(), 11.11) << endl;
	cout << useF([](double d)->double {return d / 4; }, 11.11) << endl;
	return 0;
}

#include

template
T useF(F f, T x)
{
	static int count = 0;
	cout << "count:" << ++count << endl;
	cout << "count:" << &count << endl;
	return f(x);
}
double f(double i)
{
	return i / 2;
}
struct Funtor
{
	double operator()(double d)
	{
		return d / 3;
	}
};
int main()
{
	

	function f1 = f;   //包装普通函数
	cout << f1(11.11) << endl;;
	function f2 = Funtor();  //包装仿函数
	cout << f2(11.11) << endl;
	function f3 = [](double d)->double {return  d / 4; }; //包装lamdba表达式
	cout << f3(11.11) << endl;
	return 0;
}

#include
using namespace std;
#include
int add(int x, int y)
{
	return  x + y;
}

struct Add
{
	int operator()(int x, int y)
	{
		return x + y;
	}
};
class  Puls
{
public:
	static int pulsi(int x, int y)
	{
		return x + y;
	}
	double pulsd(double x, double y)
	{
		return x + y;
	}
};


int main()
{
	function f1 = add;  //包装普通函数
	cout << f1(1, 2) << endl;
	function f2 = Add(); //包装仿函数
	cout << f2(1, 2) << endl;
	function f3 = &Puls::pulsi;  //包装成员函数可以不加&但是最好加上
	cout << f3(1, 2) << endl;

	function f4 = &Puls::pulsd;  //包装非静态函数需要增加参数,但是可以通过band来取消这个参数
	cout << f4(Puls(), 1, 2) << endl;
		 
}

逆波兰表达式求值

class Solution {
public:
    int evalRPN(vector& tokens) {
       stack st;
        for(const auto& e: tokens)
        {
            if((e != "+" && e != "-" && e != "*" && e != "/"))
            {
                st.push(stoi(e));
            }
            else
            {
                int right = st.top();
                st.pop();
                int left = st.top();
                st.pop();
                switch(e[0])
                {
                    case '+':
                    st.push(right + left);
                    break;
                    case '-':
                    st.push(left - right);
                    break;
                    case '*':
                    st.push(left * right);
                    break;
                    case '/':
                    st.push(left / right);
                    break;
                }
            }
        }
        return st.top();
    }
};

class Solution {
public:
    int evalRPN(vector& tokens) {
        unordered_map> mp;
        mp["+"] = [](int a, int b )->int{ return a + b; };
        mp["-"] = [](int a, int b )->int{ return a - b; };
        mp["*"] = [](int a, int b )->int{ return a * b; };
        mp["/"] = [](int a, int b )->int{ return a / b; };
        stack st;
        for(const auto &e : tokens)
        {
            if(mp.find(e) == mp.end())
            {
                st.push(stoi(e));
            }
            else
            {
                int right = st.top();
                st.pop();
                int left = st.top();
                st.pop();
                st.push(mp[e](left,right)); //调用包装器的方法
            }
        }
        return st.top();
    }
};

#include
int add(int a, int b)
{
	return  a - b;
}
struct Add
{
	int add(int a, int b)
	{
		return  a - b;
	}
};
int main()
{
	//调增参数位置
	function f1 = bind(add,placeholders::_1, placeholders::_2);//不绑定
	cout << f1(10, 3) << endl;
	function f2 = bind(add, placeholders::_2, placeholders::_1);//交换了参数位置
	cout << f2(10, 3) << endl;
	//调增参数个数
	functionf3 = &Add::add;
	cout << f3(Add(),10, 3) << endl;
	functionf4 = bind(&Add::add, Add(), placeholders::_1, placeholders::_2);
	cout << f4(10, 3) << endl;
}