#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int RandomGenerator(int max) {
assert(max <= RAND_MAX);
srand(time(NULL));
int a = rand() % max;
return a;
}
enum Fruit {
apple,
banana,
pear,
orange,
watermelon, // the , is not necessary
};
class Simple {
private:
int num;
public:
Simple(int a) { num = a; };
int get() { return num; };
};
struct BigInteger {
static const int BASE = 100000000;
static const int WIDTH = 8;
vector<int> s;
BigInteger(long long num = 0) { *this = num; }
BigInteger operator=(long long num) {
s.clear();
do {
s.push_back(num % BASE);
num /= BASE;
} while (num > 0);
return *this;
}
BigInteger operator=(const string &str) {
s.clear();
int x, len = (str.length() - 1) / WIDTH + 1;
for (int i = 0; i < len; i++) {
int end = str.length() - i * WIDTH;
int start = max(0, end - WIDTH);
sscanf(str.substr(start, end - start).c_str(), "%d", &x);
s.push_back(x);
}
return *this;
}
};
BigInteger a;
Fruit c = apple; // can without init
Simple b(100); // = and () both okay
int main() {
a = 12345123;
cout << b.get();
}
- 关于auto关键字:
- 在C++11前:意味着auto detect GC time,跟内存回收有关系
- 在C++11 :意味着自动判断变量类型(或函数返回类型)
- 演示
auto a = 1.0; // 自动判断类型 a 是一个double
auto a;//错误,a不能未加初始化
int compare(auto a,auto b);//错误,auto无法根据上下文推断
auto compare(int a,int b);//错误,auto无法根据上下文推断
auto compare(int a,int b) -> int;//正确,但这种用途仅为了美观
- 在C++11后 : 另有变更,此处不讨论
- 关于*this: http://www.learncpp.com/cpp-tutorial/8-8-the-hidden-this-pointer/
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