calculating user time and time elapsed

[2774]

Hi im a little bit stuck on this program im working on.

im creating a program which uses the data type Mytime the output should look something like

Enter start hh mm : 7 30

Enter finish hh mm : 7 30

Time elapsed from 07:30 until 07:30 is 00:00

2 functions have not yet been defined display1Time() & elapsed(). The program currently compiles in unix g++ i have filled the un defined function to get the program running. Basically i cant work out how to get the time displayed and the total time elapsed working. I think the time the user enters has to be converted to minutes. Can anyone help please ?

// Incomplete version
#include <iostream>
using namespace std;

struct Mytime
{
   int hours;
   int mins;
};

int timecmp(Mytime,Mytime);
// returns 0 if times are same
// returns >0 if first is later than second
// returns <0 if first is before second

int setTime(Mytime& t, int h, int m );
// if valid time sets hh and mm to h and m 
// and returns 0
// if invalid returns integer > 0 as error code
// error code +1 = underflow hours
// error code +2 = overflow hours
// error code +4 = underflow mins
// error code +8 = overflow mins

void display1Time(Mytime t);
// displays in form hh:mm

void elapsed(Mytime t1, Mytime t2, Mytime& duration);
// determines the time duration between t1 and t2
// t1 assumed to be earlier than t2

void main()
{
    Mytime now;
    Mytime then;
    Mytime howlong;
    
    int h,m;
    
    do // validate input
    {
        cout << &quot;Enter start hh mm : &quot;;
        cin >> h >> m ;
    } while (setTime(now,h,m));
    
    do
    {
        cout << &quot;Enter finish hh mm : &quot;;
        cin >> h >> m ;
    } while (setTime(then,h,m));
    
    elapsed(now,then,howlong);

    cout << &quot;Time elapsed from &quot;;
    display1Time(now);
    cout << &quot; until &quot;;
    display1Time(then);
    
    cout << &quot; is &quot;;
    display1Time(howlong);
    cout << endl;
}

int timecmp(Mytime t1,Mytime t2)
{
   if (t1.hours == t2.hours)
   {
      if (t1.mins == t2.mins)
      {
         return 0;
      }
      else // mins not same
      {
         if (t1.mins > t2.mins)
         {
            return 1; // greater than zero
         }
         else
         {
            return -1;
         }
      }
   }
   else // hours not same
   {
      if (t1.mins > t2.mins)
      {
         return 1;
      }
      else
      {
         return -1;
      }
   }
}

int setTime(Mytime& t, int h, int m )
{
    int errorCode = 0;
    if (h < 0) errorCode += 1;
    if (h > 23) errorCode += 2;
    if (m < 0) errorCode += 4;
    if (m > 59) errorCode += 8;
    if (errorCode==0){t.hours = h; t.mins = m;}
    return errorCode;
}

//////////// THE FOLLOWING FUNCTIONS ARE INCOMPLETE

void display1Time(Mytime t)
{
     cout << &quot;00:00&quot;;
}


void elapsed(Mytime t1, Mytime t2, Mytime& duration)
{
    setTime(duration,0,0);
}

 

[PhilMumf]

Hi,

The standard C library (and hence std c++ lib) provide <time.h> which has &quot;struct tm&quot; and time_t types and a number of associated functions which should allow you all the manipulation you require.

I haven't tried the following but it should work ok:

// Time(0) returns the current number of seconds
// since 1-Jan-1970. localtime converts this into
// year, month, day, hours, minutes, seconds in a
// structure. You can use gmtime to instead if you
// don't want any daylght saving applied. Anyway it
// doesn't matter here as we are going to overwrite
// the time anyway - this just sets us up a valid
// struct tm.
struct tm time1 = *(localtime(time(0)); // copies the time
struct tm time2 = time1;

// Populate the two times with the user's values
time1.tm_hour = user's time 1 hours field
time1.tm_min = user's time 1 minutes field
time2.tm_hour = user's time 2 hours field
time2.tm_min = user's time 2 minutes field

// Get the difference in seconds
// you can then process this to get the elapsed hours
// and minutes
double diff = difftime(mktime(&time2), mktime(&time1));

mktime is interesting as it corrects any invalid &quot;struct tm&quot; to a valid date time. So if you have 400 days in a year, it will correct the year to the following year and set the day appropriately. I think that it also fixes broken times.

Thus the following is valid

time_t now = time(0);
struct tm TimeStruct = *(localtime(now));
TimeStruct.tm_mdat += 100;
cout << &quot;Date/Time in 100 days is &quot; << ctime(&(mktime(TimeStruct))) << endl;

 

[2774]

thanks for the help