NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part2/18014

Internet Message Format | 1996-08-05 | 7.6 KB

Path: news.sprintlink.net!datalytics!usenet
From: Rob Stewart <[e-mail]>
Newsgroups: comp.lang.c++
Subject: Re: help with homework
Date: Thu, 18 Apr 1996 11:21:38 -0400
Organization: Datalytics, Inc
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leonel wizel wrote:
>
>     Please I need help to complete this file:   this file suppose to
> increment the object time by one second to the next hour, to the
> next minute to the next day:
>
> I need some help please:
>
> the program suppose to modify to include a tick member function
> that increments the time stored in the Time object by one second.  The
> time object should always remain in a consistent state.  The driver
> program that tests the tick member function in a loop that prints the
> time in standard format during each iteration of the loop to illustrate
> that the tick member functions workds correctly.
>
>     Incrementing into the next minute.
>     Incrementing into the next hour.
>     incrementing into the next day(i.e., 11:59:59 PM to 12:00:00 AM).
>
> //TIME3.H
>
> #ifndef TIME3_H
> #define TIME3_H
>
> class Time {
> public:
>         Time(int = 0, int = 0, int = 0);  // constructor
>
>         //set functions
>

setTime should probably return a boolean to indicate if the time
was valid, and only set the time if the input was valid.

>         void setTime(int, int, int); //set hour, minute, second

Do you really need the following three member functions?  The
setTime member function seems the most logical, since it can
handle validating all values at once.  setTime could handle
overflow of any values (like excess seconds increment minute) if
you like.

>         void setHour(int);  //set hour
>         void setMinute(int); //set minute
>         void setSecond(int); //set second
>
>         //get functions
>
>         int getHour();   //return hour
>         int getMinute(); //return minute
>         int getSecond(); //return second
>
>         void tick_increment();

It hardly seems appropriate for a Time class to know how to
print.  Rather, it should return a string (or populate a
supplied buffer) with the formatted time that the class user
could print, if desired.

Also, consider an enumerated type to indicate the desired
format:

    enum time_format
    {
        MILITARY,
        STANDARD
    };

    void    format(
            char* o_pBuffer,
            size_t i_BufferLength,
            time_format i_Format);

Of course this doesn't tell the caller how big the buffer needs
to be, and doesn't indicate if the formatting was successful.
I'll leave that part to your imagination.

>         void printMilitary();   //output military time
>         void printStandard();   //output standard time
>
> private:

Why are you using signed types for inherently unsigned values?
How about unsigned char?

>         int hour;          //0 - 23
>         int minute;        //0 - 59
>         int second;        //0 - 59
> };
>
> #endif
>
> #include "time3.h"
> #include <iostream.h>
>
> //constructor function
>
> Time::Time(int hr, int min, int sec) {setTime (hr, min, sec); }
>

The action you take here is a little odd.  Instead of forcing
values to zero if the input is invalid, how about return a
boolean to indicate whether you set the time:

bool Time::setTime(
    unsigned char i_Hour,
    unsigned char i_Minute,
    unsigned char i_Second)
{
    bool bResult = FALSE;
    if (i_Hour < 24 && i_Minute < 60 && i_Second < 60)
    {
        hour = i_Hour;
        minute = i_Minute;
        second = i_Second;
        bResult = TRUE;
    }
    return bResult;
}

> 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;
> }
>
> void Time::setHour(int h)  { hour = (h >= 0 && h < 24) ? h : 0;}
>
> void Time::setMinute(int m)
>         { minute = (m >= 60) ? m : 0; }
>
> void Time::setSecond(int s)
>         { second = (s >= 60) ? s : 0; }
>
> int Time::getHour() {return hour; }
>
> int Time::getMinute() {return minute; }
>
> int Time::getSecond() {return second; }
>
> void Time::tick_increment()
> {
>         if(second == 60)
>         {
>                 second = 0;
>                 minute++;
>         }
>                 second++;

Doesn't this next part look familiar?  Why not increment second
first, then adjust both second and minute as needed?
>                 if (second == 60)
>         {
>                 second = 0;
>                 minute++;
>         }
>                 if(minute == 60)
>         {
>                         minute = 0;
>                         hour++;
>         }
>                 if (hour == 24)
>         {

Modulo works here, but it involves a divide unecessarily.  Why
not just subtract 24?

            hour -= 24;

>                         hour %= 24;
>         }
> }

Try this instead for tick_increment (wouldn't tick be a better
name since it's like the tick of a clock?):

void Time::tick(void)
{
    second++;
    if (second > 59)
    {
        second -= 60;
        minute++;
    }
    if (minute > 59)
    {
        minute -= 60;
        hour++;
    }
    if (hour > 23)
    {
        hour -= 24;
    }
}

> void Time::printMilitary()
> {

Don't get so enamored of the ternary operator.  Your code is
less efficient when you insert a null string into cout.  Try
this instead:

    if (hour < 10)
    {
        cout << '0';
    }
    cout << hour << ':';
    if (minute < 10)
    {
        cout << '0';
    }
    cout << minute << ':';
    if (second < 10)
    {
        cout << '0';
    }
    cout << second;

When you do this, do you notice how similar all of this code is?
In other words, we need a member function to capture this
commonality:

void Time::printNumber(
    int i_Number)
{
    if (i_Number < 10)
    {
        cout << '0';
    }
    cout << i_Number;
}

So now, printMilitary becomes this:

    printNumber(hour);
    cout << ':';
    printNumber(minute);
    cout << ':';
    printNumber(second);

>         cout <<  (hour < 10 ? "0" : "") << hour << ":"
>                   << (minute < 10 ? "0" : "") << minute << ":"
>                   << (second < 10 ? "0" : "") << second;
> }
>
> void Time::printStandard()
> {
>         cout << ((hour == 0 || hour == 12) ? 12 : hour %12) << ":"
>                   << (minute < 10 ? "0" : "") << minute << ":"
>                   << (second < 10 ? "0" : "") << second
>                   << (hour < 12 ? " AM" : " PM");
> }
>
> #include <iostream.h>
> #include "time3.h"
> #include "time3.cpp"
>
> main()
> {
>   Time t;
>
>   t.setTime(23, 59, 59);
>
>   for(long int i = 1; i <= 2; i++)
>         {
>                 cout << endl << endl;
>                 cout << " Hour " << t.getHour()
>                           << " Minute " << t.getMinute()
>                           << " Second " << t.getSecond();
>
>                 cout <<"the initial time before incrementing is: " << endl
> << endl;
>
>                 t.printStandard();
>                 cout << endl;
>                 t.printMilitary();
>
>                 t.tick_increment();
>                 cout << " Hour " << t.getHour()
>                           << " Minute " << t.getMinute()
>                           << " Second " << t.getSecond()
>                           <<" the time after incrementing is: " << endl;
>
>                 t.printStandard();
>                 cout << endl;
>                 t.printMilitary();
>
>         }
>
>         return 0;
> }

Having said all that, I have to ask, what's wrong with the code?
I tested it and it seems to work correctly.  Was there something
specific you noticed that was wrong?

--
Robert Stewart        | My opinions are usually my own.
Datalytics, Inc.    | [e-mail]