2d arrays

[David Sobey]

basic question, confused by the type system of c#:

i'm making a calendar prog, with an array of days, each day being an array
of events. I want something like:

public struct Event
{
string name;
string UID;
}
private ArrayList events;
private ArrayList (events) days;

I'm aware this is kinda psuedo-code, so how should i really code this? If
necessary, the days can be a 31 sized static array.

cheers
dave

 

[Daniel O'Connell [C# MVP]]

basic question, confused by the type system of c#:

i'm making a calendar prog, with an array of days, each day being an array
of events. I want something like:

public struct Event
{
string name;
string UID;
}
private ArrayList events;
private ArrayList (events) days;

I'm aware this is kinda psuedo-code, so how should i really code this? If
necessary, the days can be a 31 sized static array.

Well, there are a number of choices. You could simply use an Event[12,31]
array or an array of ArrayLists or an ArrayList of ArrayLists, or an
ArrayList of arrays. Or you could use a hashtable. All depending on how you
want to access teh information.

Can you provide more information about what exactly you want to achieve?

 

[Champika Nirosh]

Hi,

With several reasons it is strongly advice not to use arraylist to store
value types (at least in c# for sure).. please read about object boxing /
unboxing..

Nirosh.

 

[David Sobey]

i'm basically just trying to store a list of appointments for a user, so i
can send them to a monthly calendar. number of events/appointments per day
is arbitrary of course, but i suppose i could set number of days to 31. I
think an array of arrayLists is best but not sure how to declare and
instantiate it. Is this right:

public struct Event
{
string name;
string UID;
}
ArrayList day;
day[] month;

....

days = new ArrayList();
month = new day[31];

i should just try it huh? gotta have dinner first...

thanks for your help
dave

 

[David Sobey]

how on earth to i declare and define a static array of ArrayLists? And how
would i pass this to a function. I simply cannot get my code to work:

public struct Event
{
string name;
string UID;
}
ArrayList[] month;

....
public void SetEvents(ArrayList[] list)
{
month = new ArrayList[31];
month = list.Clone();
}

It INSISTS that month is an ArrayList, which it is NOT. It's supposed to be
a static array.

 

[Stefan Simek]

I really think your best bet would be to look at Hashtables, keyed by
DateTime, pointing maybe to ArrayLists of appointments.

As for your ArrayList[] concept, the ArrayList[] itself stands for an array
of ArrayLists, or more precisely, ArrayList references. You would have to
initialize every one of the members, like:

ArrayList[] month = new ArrayList[31];

for (int day = 0; day < 31; day++)
month[day] = new ArrayList();

But as I don't think you'd like to instantiate thousands of ArrayLists in
your calendar, I'd recommend something like the following:

Hashtable calendar = new Hashtable();

ArrayList GetAppointments(DateTime date)
{
date = date.Date; // strip the time part, if any...

ArrayList appointments = calendar[date] as ArrayList;

if (appointments == null)
{
appointments = new ArrayList();
calendar[date] = appointments;
}

return appointments;
}

If you need any more help, you can also contact me directly (remove the blah
from my address)

HTH,
Stefan

 

[Daniel O'Connell [C# MVP]]

how on earth to i declare and define a static array of ArrayLists? And how
would i pass this to a function. I simply cannot get my code to work:

public struct Event
{
string name;
string UID;
}
ArrayList[] month;

...
public void SetEvents(ArrayList[] list)
{
month = new ArrayList[31];
month = list.Clone();
}

It INSISTS that month is an ArrayList, which it is NOT. It's supposed to
be a static array.

Month is an array, in this particualar circumstance. The line
ArrayList[] month;
Creates a variable named month that is typed an array of the class
ArrayList. I don't quite understand what you mean by it insisting that month
is an ArrayList. Every test I can come up with doesn't seem to fail. Infact
the only problem I can find with your code is that the call to list.Clone()
needs to be cast to ArrayList[].

Could you provide a short but complete[1] example of the issue?

1. http://www.yoda.arachsys.com/csharp/complete.html

 

[David Sobey]

actually i think you're right, just the way i was using was a bit ignorant.
thanks for your help though. i've been programming haskell lately so it's a
bit tricky, seeing the type system is so different.

cheers
dave

--
"Aristotle said that some people were
only fit to be slaves. I do not
contradict him. But I reject slavery
becase I see no people fit to be masters"
C.S Lewis

 

[Daniel O'Connell [C# MVP]]

actually i think you're right, just the way i was using was a bit
ignorant. thanks for your help though. i've been programming haskell
lately so it's a bit tricky, seeing the type system is so different.

Yes, I can certainly see that,. Fundamentally different type systems can
be hard to overcome.

I hope you've been able to fix your problem.

 

[Ravichandran J.V.]

"Aristotle said that some people were
only fit to be slaves. I do not
contradict him. But I reject slavery
becase I see no people fit to be masters"
C.S Lewis

I knew Aristotle was a brainy guy but 'gawd!', this is too much!.

with regards,


J.V.Ravichandran
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