#include <iostream>

class Log
{
public:
	const int LogLevelError = 0;
	const int LogLevelWarning = 1;
	const int LogLevelInfo = 2;
private:
	//日志实际级别
	//m开头表示类成员变量
	int m_LogLevel = LogLevelInfo;
public:
	void SetLevel(int level)
	{
		m_LogLevel = level;
	}

	//关于字符串指针，后面会讲解
	void Error(const char* message)
	{
		if (m_LogLevel >= LogLevelError)
			std::cout << "[ERROR]:" << message << std::endl;
	}

	void Warn(const char* message)
	{
		if (m_LogLevel >= LogLevelWarning)
			std::cout << "[WARNING]:" << message << std::endl;
	}

	void Info(const char* message)
	{
		if (m_LogLevel >= LogLevelInfo)
			std::cout << "[INFO]:" << message << std::endl;
	}
};

int main()
{
	Log log;
	//警告或更严重的消息会被打印出
	log.SetLevel(log.LogLevelWarning);
	log.Warn("Hello!");
	log.Error("Hello!");
	log.Info("Hello!");
	/*
	[WARNING]:Hello!
	[ERROR]:Hello!
	*/

	std::cin.get();
}

//类定义
class Player
{
	//默认是私有的
	//int x, y;
//这里的public包括了speed这个成员
public:
	int x, y;
	int speed;
};

//函数
void Move(Player& player, int xa, int ya)
{
	player.x += xa*player.speed;
	player.y += ya*player.speed;
}

int main()
{
	//player:对象
	//创建(实例化)一个对象
	Player player;
	player.x = 1;
	player.y = 2;
	player.speed = 2;
	Move(player, 1, -1);
	LOG(player.x);//3
	LOG(player.y);//0
}

//类定义
class Player
{
	//默认是私有的
	//int x, y;
//这里的public包括了speed和Move这个成员
public:
	int x, y;
	int speed;
	//方法
	void Move( int xa, int ya)
	{
		x += xa * speed;
		y += ya * speed;
	}
};



int main()
{
	//player:对象
	//创建(实例化)一个对象
	Player player;
	player.x = 1;
	player.y = 2;
	player.speed = 2;
	player.Move( 1, -1);
	LOG(player.x);//3
	LOG(player.y);//0
}

//结构定义
struct Player
{
	//默认是public的
	int x, y;
	int speed;
	//方法
	void Move( int xa, int ya)
	{
		x += xa * speed;
		y += ya * speed;
	}
};



int main()
{
	Player player;
	player.x = 1;
	player.y = 2;
	player.speed = 2;
	player.Move( 1, -1);
	LOG(player.x);//3
	LOG(player.y);//0
}

	int a = 5;
	int* b = &a;

	//&符号是类型的一部分
	//使用ref就跟使用a的别名一样
	int& ref = a;
	//这里编译器编译后会直接设置a，而
	//不会再创建一个变量
	ref = 2;

	LOG(a);

void Increment(int* value) {
	//首先引用指针，然后增加指针处的值
	(*value)++;
}

int main()
{

	int a = 5;
	Increment(&a);
	LOG(a);

	std::cin.get();
}

void Increment(int& value) {
	value++;
}

int main()
{

	int a = 5;
	Increment(a);
	LOG(a);

	std::cin.get();
}

void Increment(int& value) { 
	value++;
}

int main()
{

	int a = 5;
	int b = 8;
	//必须初始化，否则编译错误
	int& ref = a;
	
	//不会出现编译错误，但是其实没有任何效果
	ref = b;

	Increment(ref);
	LOG(b);//打印8，未改变b的值

	std::cin.get();
}

#include <iostream>
#define LOG(x) std::cout << x << std::endl

int main(){
	void* ptr=0;//0，表示这是一个无效指针
	//void* ptr=NULL;// NULL是一个# define NULL 0，其实也是0
	//void* ptr=nullptr;// c++11引入的
	std::cin.get();
}

	int var = 8;
	//void* ptr = &var;
	//int* ptr=&var;
	//double* ptr=(double*)&ptr;
	std::cin.get();

	int var = 8;

	//没有指定指针类型，编译器
	//不知道怎么存数据，*ptr=10会报错
	//void* ptr =  & var;
	//*ptr = 10;

	//指针指向的位置需要一个int大小(4字节)的
	//大小来存储数据
	int* ptr = &var;
	*ptr = 10;
	LOG(var);

	for (int i = 0; i < 5; i = i + 1) {
		Log("Hello World");
	}

	int i = 0;
	for (; i < 5; ) {
		Log("Hello World");
		i = i + 1;
	}

	int i = 0;
	bool condition = true;
	for (; condition; ) {
		Log("Hello World");
		i = i + 1;
		if (!(i < 5))
			condition = false;
	}

for(;;)
{
	
}

	int i = 0;
	while (i < 5) {
		Log("Hello World");
		i++;
	}

//执行前先判断
bool condition = false;
while (condition)
{

}

//至少执行一次
do
{

} while (condition);

#include <iostream>
int main() {
	std::cout << "Hello World!" << std::endl;
	std::cin.get();
}

#include "iostream"
#include "Log.h" 


int main() {
	//InitLog();
	int a = 8;
	a++;
	const char* string = "Hello";
	for (int i = 0; i < 5; i++) {
		const char c = string[i];
		std::cout << c << std::endl;
	}
	Log("hello world!");
	//std::cin.get();
	std::cin.get();
}

#include <iostream>

int main() {

	int variable = 8;
	std::cout << variable << std::endl;
	variable = 20;
	std::cout << variable << std::endl;
	std::cin.get();
}

	char cVariable = 'A';
	//char cVariable=65;
	//不管是用65还是'A'赋值，打印出来的都是A
	std::cout << cVariable << std::endl;
	
	
	short sVariable = 'A';
	//short cVariable=65;
	//不管是用65还是'A'赋值，打印出来的都是65
	std::cout << sVariable << std::endl;

	float fVariable = 8.2f;//4字节
	std::cout << fVariable << std::endl;
	double dVariable = 20.3;//8字节
	std::cout << dVariable << std::endl;

#include <iostream>
const char* Log(const char* message) {
	return message;
}

int Multiply(int a,int b ) { 

	Log("Multiply");
	return  a * b;
}

1>E:\cppStudyTemp\ChernoCpp\HelloWorld01\HelloWorld01\Math.cpp(10,1): error 
C2143: syntax error: missing ';' before '}' 
1>Done building project "HelloWorld01.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
========== Build completed at 17:51 and took 05.115 seconds ==========

1>MSVCRTD.lib(exe_main.obj) : error LNK2019: unresolved external symbol main referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)
1>E:\cppStudyTemp\ChernoCpp\HelloWorld01\x64\Debug\HelloWorld01.exe : fatal error LNK1120: 1 unresolved externals
1>Done building project "HelloWorld01.vcxproj" -- FAILED.