What's wrong in this line of code?

Hi,

I created a small Class that gets 1 time (format: 00:00) and minuses it from another time (same format).

This is the member function I had:

void sub(airtime t1, airtime t2)
{
int min1 = t1.hours * 60 + t1.minutes;
int min2 = t2.hours * 60 + t2.minutes;
int answer = min1 - min2;
hours = answer / 60;
minutes = answer - hours * 60;
}

At first, when I was entering certain numbers, it was crashing ( continuosly looping).

Then I changed:

int min1 = t1.hours * 60 + t1.minutes;
int min2 = t2.hours * 60 + t2.minutes;

to:

int min1 = (t1.hours * 60) + t1.minutes;
int min2 = (t2.hours * 60) + t2.minutes;

It worked perfectly when I edited the above code.

However, I still do not know what change it might have made.
I thought that in C++, the * is automatically worked before the +, so why did I need those brackets?

Thanks!
Marc

:D

Post more code.

#include <iostream.h>
#include <iomanip.h>
class airtime
{
private:
int hours;
int minutes;
public:
void set()
{
char dummy;
for( ; ; )
{
cout<<"Enter Time: (Format: 00:00)\t";
cin>>hours>>dummy>>minutes;
if ( hours <= 23 && minutes <= 59)
break;
else
cout<<"\nThe format you entered is not correct.\n\n";
};
}
void display()
{
cout<<hours<<":"<<setfill('0')<<setw(2)<<minutes;
}
void sub(airtime t1, airtime t2)
{
int min1 = (t1.hours * 60) + t1.minutes;
int min2 = (t2.hours * 60) + t2.minutes;
int answer = min1 - min2;
hours = answer / 60;
minutes = answer - hours * 60;
}
};
void main()
{
char choice;
airtime t1, t2, t3;
do
{
cout<<"Setting T1....\n";
t1.set();
cout<<"Setting T2....\n";
t2.set();
cout<<"T1 minus T2....\n";
cout<<"\nAnswer....";
t3.sub(t1,t2);
t3.display();
cout<<"\n\nWould you like to try again? y\\n?";
cin>>choice;
cout<<"\n";
}while(choice != 'n');
}

I just compiled your code, (both versions), and neither crashed with valid input. (MSVC++ 6.0).

As an observation...

>>> if ( hours <= 23 && minutes <= 59)

...your range checking is flawed, remember -1 is a perfectly valid integer...

>>>
void set()
{
char dummy;
for( ; ; )
{

>>>>

First logical error:

No need to use infinite loop here, because it breaks after you enter first hour, minute values within bounds.

Sorry, it is not necessarily logical error.

I don't see any error in your program.

>>> I don't see any error in your program.

I'm playing with it, (actually got to go now, but I was...), compile it, (either version), and when it asks for the first time enter "d" then press return!

adrianxw: try running the old code and enter: 12:06 as the first value and 3:56 and the second. It will crash :(

golem: I did that loop so that it checks that the time entered is correct. If not, it will keep looping until the user finally enters the correct input. Only then will it work well.

I don't know what was wrong. I didn't think those brackets were neccessary. But I guess they are :rolleyes: :confused:

Marc

Tried. Both versions give me 8:10. You've got problems, but I don't think they are where you think they are!

Works fine for me too..... both versions do. * is before +

Brackets
Of
Division
Multiplication
Addition
Subtraction

(i think that's right...)

I believe this applies to everything.... C++ included :)

Almosthere

>> I did that loop so that it checks that ....

Sorry again, I was confused by things out of this debate.

>> I didn't think those brackets were neccessary. But I guess they are.

No way, multiplication has precedence before addition. No brackets are needed.

hmph..then i guess only I had the problems...
hmphh..

Marc

Try this, if it helps.

#include <stdlib.h>

void sub (airtime t1, airtime t2)
{
int min1 = (t1.hours * 60) + t1.minutes;
int min2 = (t2.hours * 60) + t2.minutes;
int answer = labs (min1 - min2);
hours = answer / 60;
minutes = answer % 60;
}