CPP Note

int sum(int a, int b=20)
{
  int result;

  result = a + b;

  return result;
}
// ...
result = sum(1, 2); // 3
result = sum(1); // 21

// 有参数：[capture](parameters)->return-type{body}
[](int x, int y){ return x < y ; }

// 无参数：[capture](parameters){body}
[]{ ++global_x; } 

// 返回类型可以被明确的指定:
[](int x, int y) -> int { int z = x + y; return z + x; }

// 设置种子
srand( (unsigned)time( NULL ) );

rand();

// type arrayName [ arraySize ];
double balance[10];

double balance[5] = {1000.0, 2.0, 3.4, 17.0, 50.0};
double balance[] = {1000.0, 2.0, 3.4, 17.0, 50.0};

balance[4] = 50.0; //

int var = 20;
// int *ip = &var
int *ip;
ip = &var;

cout << "var: " << var << endl; // 20

cout << "ip: " << ip << endl; // 0x7fff50bbe874

cout << "*ip: " << *ip << endl; // 20

int *nullP = NULL;
if(!nullP){
    cout << "nullP: " << nullP << endl; // 0x0
}

int *pr;
int **ppr;
pr = &var;
ppr = ≺

funPointer(pr);
funPointer(*ppr);
int var = 20;
funPointer(&var);

void funPointer(int *p){
	cout << "[funPointer]*p: " << *p << endl;
}

int var = 20;

int *fp2p = funPointer2(&var);
cout << "*fp2p:" << *fp2p << endl;

int * funPointer2(int *p) {
    p++;
    p--;
    return p;
}

// 声明简单的变量
int    i;
double d;

// 声明引用变量
int&    r = i; // r 是一个初始化为 i 的整型引用
double& s = d; // s 是一个初始化为 d 的 double 型引用

int swapA = 1;
int swapB = 2;

swapWithRef(swapA, swapB);

void swapWithRef(int &a, int &b) {
    int temp = a;
    a = b;
    b = temp;
}

int swapA = 1;
int swapB = 2;

swapWithPointer(&swapAP, &swapBP);

void swapWithPointer(int *a, int *b){
    int temp = *a; // 局部变量temp的值为[a指针指向的值](1)
    *a = *b; // a指针指向的值改为[b指针指向的值](2)
    *b = temp; // b指针指向的值改为temp(1)
}

double vals[] = {10.1, 12.6, 33.1, 24.1, 50.0};

double &setValues(int i) {
    return vals[i];   // 返回第 i 个元素的引用
}

setValues(1) = 20.17;
cout << "vals: " << vals[1] << endl;

struct tm {
  int tm_sec;   // 秒，正常范围从 0 到 59，但允许至 61
  int tm_min;   // 分，范围从 0 到 59
  int tm_hour;  // 小时，范围从 0 到 23
  int tm_mday;  // 一月中的第几天，范围从 1 到 31
  int tm_mon;   // 月，范围从 0 到 11
  int tm_year;  // 自 1900 年起的年数
  int tm_wday;  // 一周中的第几天，范围从 0 到 6，从星期日算起
  int tm_yday;  // 一年中的第几天，范围从 0 到 365，从 1 月 1 日算起
  int tm_isdst; // 夏令时
}

time_t now = time(0); // 基于当前系统的当前日期/时间
cout << "now: " << now << endl;

char *dt = ctime(&now); // 把 now 转换为字符串形式
cout << "本地日期和时间：" << dt << endl;

// 把 now 转换为 tm 结构
tm *gmtm = gmtime(&now);
dt = asctime(gmtm);
cout << "UTC 日期和时间：" << dt << endl;

tm *ltm = localtime(&now);
// 输出 tm 结构的各个组成部分
cout << "Year: "<< 1900 + ltm->tm_year << endl;
cout << "Month: "<< 1 + ltm->tm_mon<< endl;
cout << "Day: "<<  ltm->tm_mday << endl;
cout << "Time: "<< ltm->tm_hour << ":";
cout << ltm->tm_min << ":";
cout << ltm->tm_sec << endl;

char str[] = "Hello C++";
cout << "Value of str is : " << str << endl;

char name[50];
cout << "请输入您的名称： ";
cin >> name;
cout << "您的名称是： " << name << endl;

char str[] = "Fake Error...";
cerr << "Error message: " << str << endl;

char strLog[] = "Fake Log...";
clog << "Log message: " << strLog << endl;

struct type_name {
member_type1 member_name1;
member_type2 member_name2;
member_type3 member_name3;
.
.
} object_names;

struct Books
{
   char  title[50];
   char  author[50];
   char  subject[100];
   int   book_id;
} book;

struct Book{
    char title[50];
    char author[50];
    char subject[100];
    int book_id;
};
// ...
Book book1;
strcpy(book1.title, "c++");
strcpy(book1.author, "wangjie");
strcpy(book1.subject, "c++ subject");
book1.book_id = 100;

cout << "book1 title: " << book1.title << endl;
cout << "book1 author: " << book1.author << endl;
cout << "book1 subject: " << book1.subject << endl;
cout << "book1 book_id: " << book1.book_id << endl;

void printBook(struct Book book){
    cout << "[printBook]book title: " << book.title << endl;
    cout << "[printBook]book author: " << book.author << endl;
    cout << "[printBook]book subject: " << book.subject << endl;
    cout << "[printBook]book book_id: " << book.book_id << endl;
}

Book book2;

strcpy(book2.title, "java");
strcpy(book2.author, "wangjie");
strcpy(book2.subject, "java subject");
book2.book_id = 200;

printBook(book2);

Book *book1P = &book1;
cout << "book1P->title: " << book1P->title << endl;
cout << "book1P->author: " << book1P->author << endl;
cout << "book1P->subject: " << book1P->subject << endl;
cout << "book1P->book_id: " << book1P->book_id << endl;

typedef struct
{
   char  title[50];
   char  author[50];
   char  subject[100];
   int   book_id;
}Books;

typedef long int *pint32;
pint32 x, y, z;

class Box {
public:
    double length;
    double breadth;
    double height;
};

class Box {
public:
    double length;
    double breadth;
    double height;
    // 成员函数定义
    double getVolume(void);
};

// 成员函数声明
double Box::getVolume(void){
    return this->height * this->breadth * this->length;
}

class Base {

   public:

  // public members go here

   protected:

  // protected members go here

   private:

  // private members go here

};

Box::Box(double length, double breadth, double height){
    this->length = length;
    this->breadth = breadth;
    this->height = height;
    std::cout << "box created2..." << std::endl;
}

Box::Box(double length, double breadth, double height) : length(length), breadth(breadth), height(height){
    std::cout << "box created 初始化列表..." << std::endl;
}

~Box();

Box::~Box() {
    cout << "Object is being deleted" << endl;
}

classname (const classname &obj) {
   // 构造函数的主体
}

Line( const Line &obj);      // 拷贝构造函数

Line::Line(const Line &obj){
    cout << "调用拷贝构造函数并为指针 ptr 分配内存" << endl;
    ptr = new int;
    *ptr = *obj.ptr; // 拷贝值
}

class Box
{
   double width;
public:
   double length;
   friend void printWidth( Box box );
   void setWidth( double wid );
};

// 请注意：printWidth() 不是任何类的成员函数
void printWidth( Box box )
{
   /* 因为 printWidth() 是 Box 的友元，它可以直接访问该类的任何成员 */
   cout << "Width of box : " << box.width <<endl;
}

inline int Max(int x, int y)
{
   return (x > y)? x : y;
}

cout << "Max (20,10): " << Max(20,10) << endl;
cout << "Max (0,200): " << Max(0,200) << endl;
cout << "Max (100,1010): " << Max(100,1010) << endl;

Box *boxBPr = &boxB;
cout << "*boxBPr->getVolume(): " << boxBPr->getVolume() << endl;

static int objectCount;

// 初始化类 Box 的静态成员
int Box::objectCount = 0;

cout << "static objects: " << Box::objectCount << endl;

class <派生类名>:<继承方式1><基类名1>,<继承方式2><基类名2>,…
{
<派生类类体>
};

class Rectangle: public Shape, public PaintCost{
// ...
}

void Rectangle::print(int intValue) {
    cout << "int value: " << intValue << endl;
}

void Rectangle::print(int *intValue) {
    cout << "*int value: " << *intValue << endl;
}

void Rectangle::print(double doubleValue) {
    cout << "double value: " << doubleValue << endl;
}

void Rectangle::print(const char *c) {
    cout << "char values: " << c << endl;
}

rect.print(3);
rect.print(3.3);
int intValue = 300;
rect.print(&intValue);
rect.print("hello print string.");

Box operator+(const Box&);

Box operator+(const Box&, const Box&);

Box Box::operator+(Box &b) {
    Box resultBox;
    resultBox.width = this->width + b.width;
    resultBox.height = this->height + b.height;
    resultBox.breadth = this->breadth + b.breadth;
    resultBox.length = this->length + b.length;
    return resultBox;
}

// in Shape class
virtual int getArea();

// in Rectangle class
int Rectangle::getArea() {
    cout << "Rectangle::getArea()" << endl;
    return width * height;
}

// in Triangle class
int Triangle::getArea() {
    cout << "Triangle::getArea()" << endl;
    return width * height;
}

Shape *shapePtr;
shapePtr = &rect;
cout << "&rect pointer->getArea(): " << shapePtr->getArea() << endl;
Triangle triangle(3, 4);
shapePtr = &triangle;
cout << "&triangle pointer->getArea(): " << shapePtr->getArea() << endl;

// pure virtual function
virtual int area() = 0;

const char *filePath = "/Users/wangjie/work/cpp/HelloCpp/com.wangjie.cpptest/file_temp";
ofstream outfile;
outfile.open(filePath, ios::trunc);
outfile << "temp" << endl;
outfile.close();

ifstream infile;
infile.open(filePath);
char data[100];
infile >> data;
cout << data << endl;
infile.close();

// 定位到 fileObject 的第 n 个字节（假设是 ios::beg）
fileObject.seekg( n );

// 把文件的读指针从 fileObject 当前位置向后移 n 个字节
fileObject.seekg( n, ios::cur );

// 把文件的读指针从 fileObject 末尾往回移 n 个字节
fileObject.seekg( n, ios::end );

// 定位到 fileObject 的末尾
fileObject.seekg( 0, ios::end );

double division(int a, int b)
{
   if( b == 0 )
   {
      throw "Division by zero condition!";
   }
   return (a/b);
}

#include <iostream>
#include <exception>
using namespace std;

struct MyException : public exception
{
  const char * what () const throw ()
  {
    return "C++ Exception";
  }
};

int main()
{
  try
  {
    throw MyException();
  }
  catch(MyException& e)
  {
    std::cout << "MyException caught" << std::endl;
    std::cout << e.what() << std::endl;
  }
  catch(std::exception& e)
  {
    //其他的错误
  }
}

double* pvalue  = NULL; // 初始化为 null 的指针
pvalue  = new double;   // 为变量请求内存

double* pvalue  = NULL;
if( !(pvalue  = new double ))
{
   cout << "Error: out of memory." <<endl;
   exit(1);
}

// new 与 malloc() 函数相比，其主要的优点是，new 不只是分配了内存，它还创建了对象。

delete pvalue; // 释放 pvalue 所指向的内存

// ...

char* pvalue  = NULL;   // 初始化为 null 的指针
pvalue  = new char[20]; // 为变量请求内存

delete [] pvalue;        // 删除 pvalue 所指向的数组

namespace namespace_name {
   // 代码声明
}

namespace first_space {
    void func() {
        cout << "Inside first_space" << endl;
    }
}

namespace second_space {
    void func() {
        cout << "Inside second_space" << endl;
    }
}

first_space::func();
second_space::func();

using std::cout;

namespace namespace_name {
   // 代码声明
}

template <typename T>
inline T const& maxTemplate(T const& a, T const& b){
    return a < b ? b : a;
}

cout << "maxTemplate(1, 2): " << maxTemplate(1, 2) << endl;
cout << "maxTemplate(1.0, 2.0): " << maxTemplate(1.0, 2.0) << endl;
cout << "maxTemplate(\"a\", \"b\"): " << maxTemplate("a", "b") << endl;

template <class type> class class-name {
.
.
.
}

#include <iostream>
using namespace std;

#define PI 3.14159

int main ()
{
    cout << "Value of PI :" << PI << endl; 
    return 0;
}

#define MIN(a, b) (a < b ? a : b)

cout << "#MIN(1, 2): " << MIN(1, 2) << endl;

void (*signal (int sig, void (*func)(int)))(int);

void signalHandler( int signum ){
    cout << "Interrupt signal (" << signum << ") received.\n";

    // 清理并关闭
    // 终止程序  

   exit(signum);  

}

int main (){
    // 注册信号 SIGINT 和信号处理程序
    signal(SIGINT, signalHandler);  

    while(1){
       cout << "Going to sleep...." << endl;
       sleep(1);
    }

    return 0;
}

int raise (signal sig);

void signalHandler( int signum ){
    cout << "Interrupt signal (" << signum << ") received.\n";

    // 清理并关闭
    // 终止程序 

   exit(signum);  

}

int main (){
    int i = 0;
    // 注册信号 SIGINT 和信号处理程序
    signal(SIGINT, signalHandler);  

    while(++i){
       cout << "Going to sleep...." << endl;
       if( i == 3 ){
          raise( SIGINT);
       }
       sleep(1);
    }

    return 0;
}