Question about using Date::Calc, and a general question about Perl 2

[septemberlogic]

Hi,

I've had some past experience in C++ and Java but I'm pretty new to Perl. I was trying to use the Date::Calc module, after briefly looking through the Calc.pod page on CPAN, I realized that I didn't even know how to create a new Date object. In Java, it would be something like:

Date DateName = new Date(year, month, day);

But in Date::Calc, I was not able to find a "new()" method. After playing around for a while, I realized I can declare a new date simply with the following line (correct me if I'm wrong):

$DateName = ($year, $month, $day);

This puzzled me more than it delighted me. I mean, how can you declare an object by equating it to an array? Further more, how does Perl know that I'm trying to create a Date object?

I guess I just don't get OOP in Perl yet. It would be nice if someone can explain it to me. Much thanks in advance!

 

[KevinADC]

Date::Calc is not wrtten as an OO script. It's functions are imported and called simply by their name.

Their is Date::Calc::Object if you prefer OO.

http://search.cpan.org/search?query=Date::Calc+&mode=all

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- Kevin, perl coder unexceptional!

 

[septemberlogic]

Kevin,

Thanks. Now that makes sense. So you are saying that by using the module, I'm just using its member subroutines to manipulate 3-element arrays?

Thanks again!

 

[KevinADC]

well, sort of. But this is not really an array:

($year, $month, $day);

it's a list, a list of arguments in this case. There are lots of functions in Date::Calc, some take more and some take less arguments.



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- Kevin, perl coder unexceptional!

 

[septemberlogic]

Gotcha! Thanks again!

 

[septemberlogic]

One quick question:

I have created a Date object with the following line:

$myDate = Date::Calc->today();

How do I find out which day of the week is it? One way to do so is:

print Day_of_Week($myDate->year(),$myDate->month(),$myDate->day());

but it feels like there's gotta be some easier way to do so.

Thanks!

P.S: By the way, how come I didn't need to add Date::Calc when I called the Day_of_Week() method? I only realized this after the code compiled successfully.

 

[Kirsle]

Date::Calc exported the subroutine Day_of_Week into the caller's namespace, "main::" in this case, so that you can call the function simply by calling its sub name (as if it was a sub you created yourself in your own code), as opposed to having to call "Date::Calc:ay_of_Week"

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Cuvou.com | The NEW Kirsle.net

 

[septemberlogic]

If that's the case, why did I have to use:

Date::Calc->today() instead of today()?

I tried the latter and it didn't work. Thanks Kirsle!!

 

[Kirsle]

Modules can export some functions by default, export others only when requested (eg. "use Digest::MD5 qw(md5_hex)" exports md5_hex() only when requested from the script in that way), and it can keep other ones as private-only and never export them.

Date::Calc might export some by default and others by request.

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Cuvou.com | The NEW Kirsle.net

 

[KevinADC]

module documentation usually tells what is impoted by default and what needs to be imported "manually". Not always, but the date-calc modules seem pretty well documented so I assume they do.

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- Kevin, perl coder unexceptional!

 

[septemberlogic]

Thanks Kevin! I'll check it out. What about my previous question:

I have created a Date object with the following line:

$myDate = Date::Calc->today();

How do I find out which day of the week it is? One way to do so is:

print Day_of_Week($myDate->year(),$myDate->month(),$myDate->day());

but it feels like there's gotta be some easier way to do so.

Sorry if these questions seem silly. I'm quite a Perl n00b =)

 

[KevinADC]

I don't know the answer off the top of me head. I would have to read the module documentation to find out, same as you.

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- Kevin, perl coder unexceptional!

 

[septemberlogic]

Ah I see. I will do that then! Thanks Kevin!

 

[KevinADC]

You're welcome

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- Kevin, perl coder unexceptional!