C++ time problems

dave bean · 11-22-2004, 02:13 PM

Hi
Im learning c++ but am having problems with time. I just want the simplest method (still learning and all the methods i have seen are using pointers) to represent todays date as (int date, int month, int year).

The book i have mentions using <ctime> which as i understand contains the int tm_year. I just can't work out how to initialise it . . .

ICan anyone help please ?

itsme86 · 11-22-2004, 02:56 PM

How about:

Code:

time_t now;
struct tm *t;

now = time(0);
t = localtime(&now);

Then you can use members such as t->tm_mon, t->tm_hour, etc.

dave bean · 11-23-2004, 08:32 AM

i got it working

int day = t->tm_yday;

No idea how it works or about '->' but ill guess ill figure that out as i go along

Thanks

itsme86 · 11-23-2004, 10:10 AM

Let me explain. t is a pointer to struct tm. Usually, to dereference a pointer you use the * operator. So you think you'd be able to do *t.tm_yday, but the . operator has a higher precedence that the * operator so what happens is it takes the tm_yday member of the t struct and then tries to dereference that. Clearly not what you actually want to do.

So in order to force the * operator to happen before the . operator you could do (*t).tm_yday. And that's a perfectly valid way to do it. But some wise C guru decided that dereferencing a pointer to a struct was too common and too ugly that way to not have a better solution. That's where the -> operator comes in. (*t).tm_yday is the same as doing t->tm_yday.

I hope that clears things up a bit