SPUG: Predeclaring packages

[DeRykus, Charles E]

IIUC, you could assign "our $timer" to the explictit global
inside the 'Explosive' package. You get the convenience of
'our' for $timer without exposing its value outside the 
'Explosive' package.


$Explosive::timer = 'clock';
Explosive::build();
Explosive::set();
Explosive::detonate();
exit(0);

# Master Control Program end #

package Explosive;
{
  
  our $timer = $Explosive::timer;   # expose only in 'Explosive'

  sub build { ... # include $timer # ... } 
  sub set { ... # set time on $timer # ... } 
  sub   detonate { ... # when #timer runs out # ...}

}

-- 
Charles DeRykus
 

-----Original Message-----
From: Christopher Howard [mailto:choward at indicium.us] 
Sent: Wednesday, December 31, 2008 7:37 PM
To: Seattle Perl Users Group
Subject: SPUG: Predeclaring packages

Question: Is there a way to predeclare packages, without moving the
package to a separate file?

This is my issue: When I write a script, I like to use packages to keep
everything nice and neat. And I like to have subs and packages after the
'initializing' part of the program, so it is easy to find. So what I'm
doing now is something like this:

### EXAMPLE START ###

#!/usr/bin/env perl

#sub preclarations
sub Explosive::build;
sub Explosive::set;
sub Explosive::detonate;

# Master Control Program start #

Explosive::build();
Explosive::set();
Explosive::detonate();

exit(0);

# Master Control Program end #

package Explosive;

sub build { ... }
sub set { ... }
sub detonate { ... }

### EXAMPLE END ###

This works fine. However, if I want to add package variables, with
convenient 'our' statements, I run into a problem. Say, I re-write the
program:

### EXAMPLE START ###

#!/usr/bin/env perl

#sub preclarations
sub Explosive::build;
sub Explosive::set;
sub Explosive::detonate;

# Master Control Program start #

$Explosive::timer = 'clock';

Explosive::build();
Explosive::set();
Explosive::detonate();

exit(0);

# Master Control Program end #

package Explosive;
{

our $timer;

sub build { ... # include $timer # ... } sub set { ... # set time on
$timer # ... } sub detonate { ... # when #timer runs out # ...}

}

### EXAMPLE END ###

This doesn't work because $timer is not predeclared along with the
subroutines. I can move the package to the beginning of the script, but
that is not what I want. Or I can declare $timer at the beginning of the
script separately as $Explosive::timer, but then I have to use
$Explosive::timer inside of each subroutine instead of $timer, which is
blinkin' annoying, especially if I want to change the name of the
package.

I was trying to use a goto with labels, to run through the package code
before the earlier code, but I couldn't seem to get that to work. (Maybe
it's because I'm not really sure what a label is supposed to look
like... Didn't seem to work like the examples on the internet...)

--
Christopher Howard
http://indicium.us
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