c++/oop---可变长整形数组/流插入，流提取运算符的重载

可变整型数组

查看代码

#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
class Array{
	private:
		int size;//number of element
		int *ptr;//postion
	public:
		Array (int s=0);
		Array (const Array & a);
		~Array();
		void push_back(int v);
		Array & operator =(const Array & a);
		int length(){ return size; }
		int & operator [](int i){return ptr[i];} 
};
Array::Array(int s):size(s){
	if(s==0)ptr=NULL;
	else ptr = new int [s];
}
Array::~Array(){
	if(ptr)delete [] ptr;
}
Array::Array(const Array & a){
	if(!a.ptr){
		ptr=NULL;size=0;
		return;
	}
	ptr=new int [a.size];
	memcpy(ptr,a.ptr,sizeof(int)*a.size);
	size=a.size;
}
Array & Array::operator =(const Array & a){
	if(ptr==a.ptr)return *this;//a=a;
	if(ptr)delete [] ptr;
	if(a.ptr==NULL){
		ptr=NULL;size=0;
		return *this;
	}
	ptr=new int [a.size];
	memcpy(ptr,a.ptr,sizeof(int)*a.size);
	size=a.size;
	return *this;
}
void Array::push_back(int v){
	if(!ptr){
		ptr = new int [1];	
	}
	else {
		int * tmp =new int [size+1];
		memcpy(tmp,ptr,sizeof(int)*size);
		delete [] ptr;
		ptr=tmp;
	}
	ptr[size++]=v;
}
int main(){
	Array t;
	t.push_back(1);
	t.push_back(2);
	t.push_back(3);
	cout<<t[0]<<' '<<t[1]<<' '<<t[2]<<endl;
	Array t2=t;
	cout<<t2[0]<<' '<<t2[1]<<' '<<t2[2]<<endl;
	
	return 0;
}

流插入，流提取运算符的重载

 

1.流插入运算符<<

ostream & operator <<(ostream &,自定义类 &形参对象)

istream & operator >>(istream &,自定义类 &形参对象)

只能声明为友元函数

查看代码

#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
class Complex {
	private:
	    double r,i;
	public:
	    void Print() {
	        cout << r << "+" << i << "i" << endl;
	    }
	    Complex () {}
		Complex (const char *s){
			r=0,i=0; 
			int l = strlen(s),x;
			for(x=0;x<l&&isdigit(s[x]);x++)r=r*10+s[x]-'0';
			for(x++;x<l&&isdigit(s[x]);x++)i=i*10+s[x]-'0';
		}
		friend ostream & operator << (ostream &,Complex & a);
		friend istream & operator >> (istream &,Complex & a);
};
ostream & operator << (ostream & output,Complex & a){
	output<<a.r<<'+'<<a.i<<'i'<<endl;
	return output;//continuous output
}
istream & operator >> (istream & input,Complex & a){
	input>>a.r>>a.i;
	return input;
}
int main() {
    Complex a;
    a = "3+4i"; a.Print();
    a = "5+6i"; a.Print();
    cout<<a<<endl;
    cout<<a<<'\n'<<a<<endl;
    cin>>a;
    cout<<a<<endl;
	return 0;
}

 

实现原理：

(cout.operator<<("STARWAR")).operator<<(5)

 

cout.operator<<("STARWAR") 这是个 ostream 类型的引用，其实就是 cout 的引用