Start with Chrono.h and Chrono.cpp ; for now put a dummy \" return sunday; \" or
ID: 3838049 • Letter: S
Question
Start with Chrono.h and Chrono.cpp ; for
now put a dummy "return sunday;" or "return d;" in the last 3 functions on
pages 337-338. Add a prefix ++ operator to the Date class by putting the
declaration in the Date class in Chrono.h and the definition in Chrono.cpp.
The prefix ++ operator should change a date to "tomorrow" using the following
pseudocode:
Date& operator++(){
//add 1 to d //tomorrow, unless we were at the end of the month
//if is_date is false
// //need to change to first of next month
// set d to 1
// if m is December
// //need to change to next year too
// set m to January
// increment y
// else
// increment m
return *this;
}
Write a main which repeatedly reads a Date with cin >> in a while statement, increments the Date with your ++, and prints "Tomorrow is" and the
new value of the Date using cout <<.
------------------------------------------------------------------------------------------------------------------
// file Chrono.h
namespace Chrono {
enum class Month {
jan=1, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec
};
class Date {
public:
class Invalid { }; // to throw as exception
Date(int y, Month m, int d); // check for valid date and initialize
Date(); // default constructor
// the default copy operations are fine
// nonmodifying operations:
int day() const { return d; }
Month month() const { return m; }
int year() const { return y; }
// modifying operations:
void add_day(int n);
void add_month(int n);
void add_year(int n);
private:
int y;
Month m;
int d;
};
bool is_date(int y, Month m, int d); // true for valid date
bool leapyear(int y); // true if y is a leap year
bool operator==(const Date& a, const Date& b);
bool operator!=(const Date& a, const Date& b);
ostream& operator<<(ostream& os, const Date& d);
istream& operator>>(istream& is, Date& dd);
Day day_of_week(const Date& d); // day of week of d
Date next_Sunday(const Date d); // next Sunday after d
Date next_weekday(const Date& d); // next weekday after d
} // Chrono
// Chrono.cpp
#include "Chrono.h"
namespace Chrono {
// member function definitions:
Date::Date(int yy, Month mm, int dd)
: y{yy}, m{mm}, d{dd}
{
if (!is_date(yy,mm,dd)) throw Invalid{};
}
const Date& default_date()
{
static Date dd {2001,Month::jan,1}; // start of 21st century
return dd;
}
Date::Date()
:y{default_date().year()},
m{default_date().month()},
d{default_date().day()}
{
}
void Date:: add_day(int n)
{
// . . .
}
void Date::add_month(int n)
{
// . . .
}
void Date::add_year(int n)
{
if (m==feb && d==29 && !leapyear(y+n)) { // beware of leap years!
m = month::mar; // use March 1 instead of February 29
d = 1;
}
y+=n;
}
// helper functions:
bool is_date(int y, Month m, int d)
{
// assume that y is valid
if (d<=0) return false; // d must be positive
if (m<Month::jan || Month::dec<m) return false;
int days_in_month = 31; // most months have 31 days
switch (m) {
case Month::feb: // the length of February varies
days_in_month = (leapyear(y))?29:28;
break;
case Month::apr: case Month::jun: case Month::sep: case Month::nov:
days_in_month = 30; // the rest have 30 days
break;
}
if (days_in_month<d) return false;
return true;
}
bool leapyear(int y)
{
// see exercise 10
}
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);
}
ostream& operator<<(ostream& os, const Date& d)
{
return os << '(' << d.year()
<< ',' << d.month()
<< ',' << d.day() << ')';
}
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!=')') { // oops: format error
is.clear(ios_base::failbit); // set the fail bit
return is;
}
dd = Date(y, Month(m),d); // update dd
return is;
}
enum class Day {
sunday, monday, tuesday, wednesday, thursday, friday, saturday
};
Day day_of_week(const Date& d)
{
// . . .
}
Date next_Sunday(const Date& d)
{
// ...
}
Date next_weekday(const Date& d)
{
// . . .
}
} // Chrono
Explanation / Answer
Date& Date::operator++()
{
//add 1 to d //tomorrow, unless we were at the end of the month
++d;
//if is_date is false
if (is_date == false){
// //need to change to first of next month
// set d to 1
d = 1;
// if m is December
if(m == dec){
// //need to change to next year too
// set m to January
m = jan;
// increment y
++y;
}
// else
else {
m = Month(int(m) + 1);
}
}
// increment m
return *this;
}
main function:-
#include "stdafx.h"
#include<iostream>
#include "Chrono.h"
#include "Chrono.cpp"
using namespace std;
int main(){
Chrono::Date today;
std::cout << "Enter the the date: ";
std::cin >> today;
++today;
std::cout << "Tomorrow is " << today << endl;
system("pause");
return 0;
}
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