[capture list] (params list) mutable exception-> return type { function body }            

表达式中各个参数的含义如下：
[capture list]:外部变量列表         (表示外部传进来的数值)
(params list):形参列表             (比如用for_each传进来的数值)
mutable:表示能不能修改捕获的变量     (可省略)
exception:异常设定                  (可省略)         
return type:返回类型                (可省略)
function body:函数体     

#include <iostream>
#include <vector>
#include <set>
#include <algorithm>

using namespace std;

void myPrintf(int elem)
{
	cout << elem << " ";
}

int main()
{
	vector<int> vec(5);
	int i = 1;
	int num = 0;
	cout << "-----------通过外部参数给vec赋值，num改变，i不改变----------" << endl;
	generate(vec.begin(), vec.end(), [i, &num]() {
		num = i * i + num;
		return num;
	});
	cout << "-----------值传递和引用传递的区别----------" << endl;
	cout << "i = " << i << "  num = " << num << endl;
	cout << "-----------打印vec中的值----------" << endl;
	for_each(vec.begin(), vec.end(), [](int i) {
		cout << i<<" "; 
	});
	cout << endl;

	cout << "-----------传递外部变量和形参，引用传递则改变外部变量----------" << endl;
	int total = 0;
	for_each(vec.begin(), vec.end(), [&total](int i) {
		total += i;
	});
	cout << "total = " << total << endl;

	cout << "-----------形参以值传递方式，实参的数值不改变----------" << endl;
	int num1 = 10;
	int num2 = 5;
	for_each(vec.begin(), vec.end(), [=](int x) {
		x = x * num1 + num2;
		cout << "x = " << x << endl;
	});
	//vec中的数值未改变
	for_each(vec.begin(), vec.end(), myPrintf);//可用myPrintf函数来打印输出，也可用lambda来打印
	cout << endl;
	cout << "-----------形参以引用传递方式，实参的数值会改变----------" << endl;
	for_each(vec.begin(), vec.end(), [=](int &x) {
		x = x * num1 + num2;
		cout << "x = " << x << endl;
	});
	//vec中的数值改变
	for_each(vec.begin(), vec.end(), myPrintf);
	cout << endl;

	cout << "-----------删除digits中等于blacklist的数值----------" << endl;
	std::set<int> blacklist = { 7, 8, 9 };
	std::vector<int> digits = { 3, 9, 1, 8, 4, 7, 1 };
	digits.erase(std::remove_if(digits.begin(), digits.end(), [blacklist](int i) {
		return blacklist.find(i) != blacklist.end();
	}),
		digits.end());
	for (auto i : digits)
		cout << i << endl;
}