date1.cpp

来自「经典vc教程的例子程序」· C++ 代码 · 共 104 行

// Fig. 8.6: date1.cpp
// Member function definitions for Date class
#include <iostream.h>
#include "date1.h"

// Initialize static member at file scope; 
// one class-wide copy.
const int Date::days[] = { 0, 31, 28, 31, 30, 31, 30,
                           31, 31, 30, 31, 30, 31 };

// Date constructor
Date::Date( int m, int d, int y ) { setDate( m, d, y ); }

// Set the date
void Date::setDate( int mm, int dd, int yy )
{
   month = ( mm >= 1 && mm <= 12 ) ? mm : 1;
   year = ( yy >= 1900 && yy <= 2100 ) ? yy : 1900;

   // test for a leap year
   if ( month == 2 && leapYear( year ) )
      day = ( dd >= 1 && dd <= 29 ) ? dd : 1;
   else
      day = ( dd >= 1 && dd <= days[ month ] ) ? dd : 1;
}

// Preincrement operator overloaded as a member function.
Date &Date::operator++()
{
   helpIncrement();
   return *this;  // reference return to create an lvalue
}

// Postincrement operator overloaded as a member function.
// Note that the dummy integer parameter does not have a
// parameter name.
Date Date::operator++( int )
{
   Date temp = *this;
   helpIncrement();

   // return non-incremented, saved, temporary object
   return temp;   // value return; not a reference return
}

// Add a specific number of days to a date
const Date &Date::operator+=( int additionalDays )
{
   for ( int i = 0; i < additionalDays; i++ )
      helpIncrement();

   return *this;    // enables cascading
}

// If the year is a leap year, return true; 
// otherwise, return false
bool Date::leapYear( int y )
{
   if ( y % 400 == 0 || ( y % 100 != 0 && y % 4 == 0 ) )
      return true;   // a leap year
   else
      return false;  // not a leap year
}

// Determine if the day is the end of the month
bool Date::endOfMonth( int d )
{
   if ( month == 2 && leapYear( year ) )
      return d == 29; // last day of Feb. in leap year
   else
      return d == days[ month ];
}

// Function to help increment the date
void Date::helpIncrement()
{
   if ( endOfMonth( day ) && month == 12 ) {  // end year
      day = 1;
      month = 1;
      ++year;
   }
   else if ( endOfMonth( day ) ) {            // end month
      day = 1;
      ++month;
   }
   else       // not end of month or year; increment day
      ++day;
}

// Overloaded output operator
ostream &operator<<( ostream &output, const Date &d )
{
   static char *monthName[ 13 ] = { "", "January",
      "February", "March", "April", "May", "June",
      "July", "August", "September", "October",
      "November", "December" };

   output << monthName[ d.month ] << ' '
          << d.day << ", " << d.year;

   return output;   // enables cascading
}