clocks2.cpp

C++ 这是国外计算机科学教材系列《big C++》书籍的源代码ch

#include <iostream>
#include <iomanip>
#include <string>

using namespace std;

#include "ccc_time.h"

class Clock
{
public:
   /**
      Constructs a clock that can tell the local time.
      @param use_military true if the clock uses military format
   */
   Clock(bool use_military);
   
   /**
      Gets the location of this clock.
      @return the location
   */
   string get_location() const;

   /**
      Gets the hours of this clock.
      @return the hours, in military or am/pm format
   */
   int get_hours() const;

   /**
      Gets the minutes of this clock.
      @return the minutes
   */
   int get_minutes() const;

   /**
      Checks whether this clock uses miltary format.
      @return true if miltary format
   */
   bool is_military() const;
private:
   bool military;
};

Clock::Clock(bool use_military)
{
   military = use_military;
}

string Clock::get_location() const
{
   return "Local";
}

int Clock::get_hours() const
{
   Time now;
   int hours = now.get_hours();
   if (military) return hours;
   if (hours == 0) 
      return 12;
   else if (hours > 12)
      return hours - 12;
   else
      return hours;
}

int Clock::get_minutes() const
{
   Time now;
   return now.get_minutes();
}

bool Clock::is_military() const
{
   return military;
}

class TravelClock : public Clock
{
public:
   /**
      Constructs a travel clock that can tell the time
      at a specified location
      @param mil true if the clock uses military format
      @param loc the location
      @param diff the time difference from the local time
   */
   TravelClock(bool mil, string loc, int diff);
   string get_location() const;
   int get_hours() const;
private:
   string location;
   int time_difference;
};

TravelClock::TravelClock(bool mil, string loc, int diff)
   : Clock(mil)
{
   location = loc;
   time_difference = diff;
   while (time_difference < 0) 
      time_difference = time_difference + 24;
}

string TravelClock::get_location() const
{
   return location;
}

int TravelClock::get_hours() const
{
   int h = Clock::get_hours();
   if (is_military())
      return (h + time_difference) % 24;
   else
   {
      h = (h + time_difference) % 12;
      if (h == 0) return 12;
      else return h;
   }
}

int main()
{
   Clock clock1(true);
   TravelClock clock2(true, "Rome", 9);
   TravelClock clock3(false, "Tokyo", -7);

   cout << clock1.get_location() << " time is " 
      << clock1.get_hours() << ":"
      << setw(2) << setfill('0') 
      << clock1.get_minutes() 
      << setfill(' ') << "\n";
   cout << clock2.get_location() << " time is " 
      << clock2.get_hours() << ":"
      << setw(2) << setfill('0') 
      << clock2.get_minutes() 
      << setfill(' ') << "\n";
   cout << clock3.get_location() << " time is " 
      << clock3.get_hours() << ":"
      << setw(2) << setfill('0') 
      << clock3.get_minutes() 
      << setfill(' ') << "\n";
   return 0;
}