cppReview

namespace scope

#include<iostream>
namespace Yahoo{
    char* homePageUrl;
}
namespace Google{
    char* homePageUrl;
}
using namespace Google;
using Google::homePageUrl;
int main(){
    Yahoo::homePageUrl ="a";
    homePageUrl ="b";
    return 0;
}

Data declarartion in cpp

#include <iostream>

const int MAX = 500;
enum semester{SUMMER=0,FALL,SPRING};
int main(){
    semester x = SUMMER;
    return 0;
}

Pointer and Reference

int main(){
    int a=5;
    int *b=&a; // pointer : the memory address of an object
    int &c=a; // reference : an alternative name to an object
    return 0;
}

File I/O in c++

#include <iostream>
#include <fstream>

using namespace std;

int main(){
    ofstream outFile("my.out",ios::out);
    if(!outFile){
        cout<<"cannot open my.out"<<endl;
        return 1;
    }
    int n = 50;
    outFile<<n<<endl;
}

#include <iostream>
#include <fstream>

using namespace std;

int main(){
    ifstream inFile("my.out",ios::in);
    if(!inFile){
        cout<<"cannot open my.out"<<endl;
        return 1;
    }
    int n;
    while (!inFile.eof())
    {
        inFile >> n;
        cout<<n<<endl;
    }
}

I/O Operator Overloading

#include <iostream>
#include <fstream>

using namespace std;

class Ferrari{
public:
    int W,H,L;
    char* model;

/***key code***/
    // friend ostream& operator<<(ostream &os, const Ferrari &obj){
    //     os<<"************"<<endl;
    //     os<<"Ferrari"<<obj.model<<endl;
    //     os<<"W"<<obj.W<<endl;
    //     os<<"H"<<obj.H<<endl;
    //     os<<"L"<<obj.L<<endl;
    // }
};
/***alternative key code***/
ostream& operator<<(ostream &os, const Ferrari &obj){
        os<<"************"<<endl;
        os<<"Ferrari"<<obj.model<<endl;
        os<<"W"<<obj.W<<endl;
        os<<"H"<<obj.H<<endl;
        os<<"L"<<obj.L<<endl;
}
int main(){
    Ferrari myCar;
    myCar.model=(char*)"car";
    cout<<myCar<<endl;
    return 0;
}

Function in C++

inline: compiler replaces each function using its function body.

inline int sum(int a,int b){
    return a+b;
}

Parameter Passing

• by Value
• by Pointer
• by reference

Passing const arguments

void func(const dataType& a){}

Function Overloading in C++

define two functions of same function name

int Max(int,int);
int Max(int,int,int);
int Max(float,int);

Polymorphism in C++

相同的函数名、参数类型、返回类型

#include <iostream>
using namespace std;

class Shape{
protected:
    int width,height;
public:
    Shape(int w=0,int h=0){
        width=w;
        height=h;
    }
    /***key code***/
    virtual int area()=0;
};
//正方形
class Rectangle:public Shape{
public:
    Rectangle(int w,int h):Shape{w,h}{}
    int area(){
        return width*height;
    }
};
//三角形
class Triangle:public Shape{
public:
    Triangle(int w,int h):Shape{w,h}{} //构造函数初始化
    int area(){
        return width*height/2;
    }
};
int main(){
    Shape * shape = new Rectangle(1,2);
    cout<<shape->area()<<endl;
    shape = new Triangle(1,2);
    cout<<shape->area()<<endl;
    return 0;
}

Dynamic Memory Allocation(分配) in c++

malloc、delete、realloc、memset、memcopy
new、delete

int main(){
    int* x=(int*)malloc(sizeof(int));
    free(x);

    int* y = new int;
    delete y;

    int *data = new int[10];
    delete []  data;
    return 0;
}

Handling Exception

#include <iostream>
using namespace std;

int DivZero(int a,int b){
    if(a<=0||b<<0)
        throw "All parameters should be > 0";
    return a/b;
}

int main(){
    try
    {
        cout<<DivZero(5,5)<<endl;
    }
    catch(const char * e){
        cout<<"error"<<e<<endl;
    }
    // catch(const std::exception& e)
    // {
    //     std::cerr << e.what() << '\n';
    // }
    return 0;
}

Type of Constructors

• Default constructor

Rectangle();

• Augmented constructor

Rectangle(int,int,int,int);

Rectangle::Rectangle(int x,int y,int h,int w){
	xLow=x;yLow=y;
	height=h;width=w;
}

May use member initialization list(more efficient)

Rectangle::Rectangle(int x,int y,int h,int w):xLow(x),yLow(y),height(h),width(w){}

• Copy constructor

Rectangle(const Rectangle&);

Rectangle::Rectangle(const Rectangle& _src){
	xLow=_src.xLow;
	yLow=_src.y_Low;
	height=_src.height;
	width=_src.width;
}

Operator Overloading

#ifndef RECTANGLE_H
#define RECATANGLE_H
class Rectangle{
	Rectangle();
	~Rectangle();
	bool operator==(const Rectanfle&);
	Rectagle& operator(const Rectangle&);
}
#endif

Template in C++

A mechanism to parameterize the target data type and instantiate it to a proper(恰当的) data type in compline time.

Function Template

template <class T>
T sum(T* data,const int SIZE){
	T sum=0;
	for(int i=0;i<SIZE;i++){
		sum+=data[i];
	}
	return sum;
}

Class Template

emplate<class T> 
struct Z // template definition
{
    void f() {}
    void g(); // never defined
}; 
template struct Z<double>; // explicit(明确的,显式的) instantiation of Z<double>
Z<int> a; // implicit(含蓄的，隐式的) instantiation of Z<int>
Z<char>* p; // nothing is instantiated here
p->f(); // implicit instantiation of Z<char> and Z<char>::f() occurs here.
// Z<char>::g() is never needed and never instantiated: it does not have to be defined

C++ Inheritance

Overloading(重载)相同函数名称 v.s. Overriding(重写)继承中

Standard C++ Library

file,stirng

C++ STL(Standard template library)

algrithms, data structure like vector, list, queues and stacks.