date1.cpp

《c＋＋大学教程实验指导书》源码

// P10_12: date1.cpp
// Date class member function definitions.
#include <iostream>
#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 ); 

} // end Date constructor

// set month, day and year
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;

} // end function setDate

// overloaded preincrement operator 
Date &Date::operator++()
{
   helpIncrement();

   return *this;  // reference return to create an lvalue

} // end function operator++

// overloaded postincrement operator; note that the dummy 
// integer parameter does not have a parameter name
Date Date::operator++( int )
{
   Date temp = *this;
   helpIncrement();  // hold current state of object

   // return unincremented, saved, temporary object
   return temp;   // value return; not a reference return

} // end function operator++

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

   return *this;    // enables cascading

} // end function operator+=

// return month
int Date::getMonth() const
{
   return month;

} // end function getMonth

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

} // end function leapYear

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

} // end function endOfMonth

// function to help increment the date
void Date::helpIncrement()
{
   // day is not end of month
   if ( !endOfMonth( day ) )
      ++day;

   else 
      
      // day is end of month and month < 12
      if ( month < 12 ) {
         ++month;
         day = 1;
      }

      // last day of year
      else {
         ++year;
         month = 1;
         day = 1;
      }

} // end function helpIncrement

// 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

} // end function operator<<



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