fig06_03.cpp

《c＋＋大学教程》源码

// Fig. 6.3: fig06_03.cpp
// Time class.
#include <iostream>

using std::cout;
using std::endl;

#include <iomanip>

using std::setfill;
using std::setw;

// Time abstract data type (ADT) definition
class Time {

public:
   Time();                        // constructor
   void setTime( int, int, int ); // set hour, minute, second
   void printUniversal();         // print universal-time format
   void printStandard();          // print standard-time format

private:
   int hour;     // 0 - 23 (24-hour clock format)
   int minute;   // 0 - 59
   int second;   // 0 - 59

}; // end class Time

// Time constructor initializes each data member to zero and
// ensures all Time objects start in a consistent state
Time::Time() 
{ 
   hour = minute = second = 0; 

} // end constructor Time

// set new Time value using universal time, perform validity
// checks on the data values and set invalid values to zero
void Time::setTime( int h, int m, int s )
{
   hour = ( h >= 0 && h < 24 ) ? h : 0;
   minute = ( m >= 0 && m < 60 ) ? m : 0;
   second = ( s >= 0 && s < 60 ) ? s : 0;

} // end function setTime

// print Time in universal format
void Time::printUniversal()
{
   cout << setfill( '0' ) << setw( 2 ) << hour << ":"
        << setw( 2 ) << minute << ":"
        << setw( 2 ) << second;

} // end function printUniversal

// print Time in standard format
void Time::printStandard()
{
   cout << ( ( hour == 0 || hour == 12 ) ? 12 : hour % 12 )
        << ":" << setfill( '0' ) << setw( 2 ) << minute
        << ":" << setw( 2 ) << second 
        << ( hour < 12 ? " AM" : " PM" );

} // end function printStandard

int main()
{
   Time t;  // instantiate object t of class Time

   // output Time object t's initial values
   cout << "The initial universal time is ";
   t.printUniversal();  // 00:00:00
   
   cout << "\nThe initial standard time is ";
   t.printStandard();   // 12:00:00 AM

   t.setTime( 13, 27, 6 );   // change time

   // output Time object t's new values
   cout << "\n\nUniversal time after setTime is ";
   t.printUniversal();  // 13:27:06
   
   cout << "\nStandard time after setTime is ";
   t.printStandard();   // 1:27:06 PM

   t.setTime( 99, 99, 99 );  // attempt invalid settings

   // output t's values after specifying invalid values
   cout << "\n\nAfter attempting invalid settings:"
        << "\nUniversal time: ";
   t.printUniversal();  // 00:00:00
   
   cout << "\nStandard time: ";
   t.printStandard();   // 12:00:00 AM
   cout << endl;

   return 0; 

} // end main

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