C++ - Date

1、使用C++ 实现一个Date类

 

namespace Chrono{
	
	class Date{
		public:
			enum Month{
				jan=1,feb,mar,apr,may,jun,jul,aug,sep,oct,nov,dec
			};
			
			class Invalid{}; //to throw as exception
			
			Date(int y,Month m,int d);
			Date();
			
			int day() const {return d;}
			Month month() const {return m;}
			int year() const {return y;}
			
			void add_day(int n);
			void add_month(int n);
			void add_year(int n);
			
		private:
			int y;
			Month m;
			int d;
	};
	
	/* helper functions: */ 
	bool is_date(int y,Date::Month m,int d);
	bool leapyear(int y);  //是否闰年
	bool operator==(const Date& a,const Date& b);
	bool operator!=(const Date& a,const Date& b);
	istream& operator>>(istream& is,Date& dd);
	ostream& operator<<(ostream& os,const Date& d);
}

　　

#include "chrono.h"

namespace Chrono{
    Date::Date(int yy,Month mm,int dd):y(yy),m(mm),d(dd)
    {
        if(!is_date(yy,mm,dd))
            throw Invalid();
    }
    
    //default_date() 用来代替全局变量 
    Date& default_date(){
        static Date dd(2000,Date::jan,1);
        return dd;
    }
    
    int days_in_month(int y,Date::Month m){
        switch(m){
            case Date::feb:
                return (leapyear(y))?29:28;
            case Date::apr:
            case Date::jun:
            case Date::sep:
            case Date::nov:
                return 30;
            default:
                return 31;
        }
    }
    
    Date::Date()
        :y(default_date().year()),
        m(default_date().month()),
        d(default_date().day())
    {
    }
    
    void Date::add_day(int n){
        while(n>=days_in_month(y,m)){
            n-=days_in_month(y,m);
            add_month(1);
        }
        if(d+n>days_in_month(y,m)){
            d=d+n-days_in_month(y,m);
            add_month(1);
        }else{
            d+=n;
        }
    }
    
    void Date::add_month(int n){
        bool flag=d==days_in_month(y,m);
        while(n>0){
            if(m==dec){
                m=jan;
                add_year(1);
            }else{
                m=(enum Month)(m+1);
            }
            n--; 
        }
        if(flag){
            d=days_in_month(y,m);
        }
    }
    
    void Date::add_year(int n){
        if(m==feb&&d==29&&!leapyear(y+n)){
            m=mar; //use March 1 instead of feb 29 
            d=1;
        }
        y+=n;
    }
    
    bool is_date(int y,Date::Month m,int d){
        if(d<=0) return false;
        if(d>days_in_month(y,m)) return false;
        return true;
    }
    
    bool leapyear(int y){
        if(y<=0) return false;        
        if(y%4==0){
            if(y%100==0 && y%400!=0) return false;
            return true;
        }
        return false;
    }
    
    bool operator==(const Date& a,const Date& b){
        return    a.year()==b.year() &&
                a.month()==b.month() &&
                a.day()==b.day();    
    }
    
    bool operator!=(const Date& a,const Date& b){
        return !(a==b); 
    }
    
    istream& operator>>(istream& is,Date& dd){
        int y,m,d;
        char ch1,ch2,ch3,ch4;

        is>>ch1>>y>>ch2>>m>>ch3>>d>>ch4;
        if(!is) return is;
        if(ch1!='('||ch2!=','||ch3!=','||ch4!=')'){
            is.clear(ios_base::failbit);
            return is;
        }
        
        return is;
    }
    
    ostream& operator<<(ostream& os,const Date& d){
        return os<<'('<<d.year()
        <<','<<d.month()
        <<','<<d.day()<<')'; 
    }
}