[prog] C language: structures containing structures

[aec]

On Wed, Nov 03, 2004 at 02:06:51PM -0600, Meredith L. Patterson wrote:
> 
> Take a look at the prototype for timekeeper():
> 
> > struct dateAndTime timekeeper(struct dateAndTime current)
> 
> later.sDate is a date struct; the function requires a dateAndTime 
> struct. If you just pass in later, you should be fine.
> 
> >This is topic is not clealy discussed in my C book so Im kinda
> >confused at the moment. 
> 
> It's a level of indirectness, which is always a bit confusing -- I've 
> run into the same problem plenty of times myself. FWIW, this is often a 
> good reason to define accessor functions when you plan to operate on the 
> guts of a data structure; that way, you can quickly check the return 
> type rather than having to dig through your code.
> 
> (This isn't actually so helpful in C, because structs can't have member 
> functions, but you could have something like
> 
>   date getDate(struct dateAndTime foo) {
> 	return foo.sDate;
>   }
>   time getTime(struct dateAndTime foo) {
> 	return foo.sTime;
>   }
> 
> Then, later on, when you wanted to call timekeeper(), if you called it like
> 
> 	timekeeper(getDate(later));
> 
> the fact that getDate()'s return type is date should throw you a red 
> flag saying "whoops, I'm passing the wrong parameter type to 
> timekeeper()!" Anyway, it's much more useful in C++, where you can give 
> member functions to classes (so you'd have syntax like later.getDate()), 
> but you can do it in C anyway if you want to.)
> 
> Hope this helps!
> 
yes thank you it did help, I should really have seen that at this
point in the game but I didnt. 

 later = timekeeper(today); 

 gives me the result I wanted.

orchid at supergrass C $ ./a.out 
3/30/0	2:1:2004
4/31/1	3:2:2005

I will try the other method you suggest too.

-- 
Angelina Carlton