C++仿函数

---

---

仿函数[bool 谓词和二元谓词]

参数有一个的返回值为bool的数据类型，为一元谓词
参数有两个的返回值为bool的数据类型，二元谓词

#include 
#include 
#include 
#include
using namespace std;
//仿函数 返回值为bool的数据类型 为谓词
class stu {
public:
	//参数有一个的时一元谓词
	bool operator()(int val) {
		return val > 5;
	}
	bool operator()(int val1, int val2) {
		return val1 > val2;
	}
	
};
void show(vector <int> ret) {
	for (auto a : ret)
		cout << a << "   ";
}
int main() {
	vector <int>ret;
	for (int i = 0; i < 10; i++) {
		ret.push_back(rand() % 100);
	}
	//vector ::iterator
	auto isok = find_if(ret.begin(), ret.end(), stu());
	if (isok == ret.end())
		cout << "没找到" << endl;
	else
		cout << "找到了" << *isok << endl;
	sort(ret.begin(), ret.end(), stu());
	show(ret);
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35

算术仿函数 include functional

一元运算符

negate

二元运算符

• ‘+’ plus
• ‘-’ minus
• ‘x’ multiplies
• ‘/’ divides
• '%'modulus

#include 
#include 
#include
#include 
using namespace std;

void test01() {
	negate <int> n;//取反
	cout << n(50)<<endl;
}
void test02() {
	plus <int> n;
	cout << n(10, 20)<<endl;
}
int main() {
	test01();
	test02();
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

关系仿函数[头文件functional]

大于 greater
大于等于 geater_equal
小于 less
小于等于 less_equal
等于 equal_to
不能与 not_equal_to

#include 
#include 
#include
#include 
using namespace std;

void show(vector <int> &ret) {
	for (vector<int>::iterator it = ret.begin(); it != ret.end(); it++)
		cout << *it << "   ";
	cout << endl;
}
vector <int> init() {
	vector <int> ret;
	for(int i=0;i<10;i++)
		ret.push_back(rand() % 50);
	return ret;
}
int main() {
	vector <int> ret;
	ret = init();
	show(ret);
	//内建函数对象  greater用于排序
	sort(ret.begin(), ret.end(), greater<int>());
	show(ret);
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

逻辑仿函数

logical_and 和
logical_not 非
logical_or 或

#include 
#include 
#include
#include 
using namespace std;

void show(vector <bool>ret) {
	for (vector<bool>::iterator it = ret.begin(); it != ret.end(); it++)
		cout << *it << "   ";
	cout << endl;
}
vector <bool> init() {
	vector <bool> ret;
	for(int i=0;i<10;i++)
		ret.push_back(rand() % 2);
	return ret;
}
int main() {
	vector <bool> ret;
	ret = init();
	show(ret);
	//内建函数对象  greater用于排序
	vector <bool>ret1(ret);
	transform(ret.begin(), ret.end(),ret1.begin(),logical_not<bool>());
	show(ret1);
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26