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Postings from April 2002
From: "Jason Frisvold" <Jason.Frisvold@corp.ptd.net>
> Judging from the subject lines coming across the list today, I think
> I'm gonna toss this question out there and then duck and cover... :-)
We do not shoot at people here. Even if they do provide the missile
address. ;-)
> Question #1.
>
> When I'm writing code, I want to be able to view as much output as
> possible so I can trace through everything and ensure that it is,
> indeed, running correctly. I've gone as far as writing my own debug
> module that uses "levels" and outputs everything in color.
> (Term::ANSIColor is a lot of fun to play with)... One major side
> effect of this is that my code will begin to run slower due to all of
> the debugging...
>
> So, the obvious answer is to turn off the debugging. However, even
> with my magic "debug off switch" (see below for a better explanation),
> the calls to the debug routines are still being made. Is there any
> sort of #IFDEF that can be done in perl, or do I actually have to
> comment out (or remove) each call?
>
> My magic "debug off switch" is nothing more than a simple if/then
> statement. It works on the principle that if $IDebugLevel is a
> positive integer greater than 0, then I want to debug.
You may mark them somehow and then process your script with
something that'll comment them out or strip them entirely.
Like http://Jenda.Krynicky.cz/perl/mversion.pl.txt
> Question #2.
>
> Relating to the debugging, there are several instances where I have
> variables that are only defined based on the definition of other
> variables that exist elsewhere. Kind of like :
>
> sub dummy {
> if ($a == 10) { my $b = 0; }
> }
>
> $b is a local variable, so whenever the subroutine is exited, $b
> vanishes into the ether.
In this case the difference is not visible, but still ... please keep in
mind that the scope of a variable is a block, not a subroutine!
So
sub foo {
if (1 > 2) {
my $x = 1;
}
print "\$x=$x\n";
}
foo();
will NOT print
$x=1
I hope you DO
use strict;
> The problem is that I have $b in several
> debug statements because I want to see it when it's used, but I don't
> want to have to create a huge if/then structure to determine what
> variables are being used.
No you cannot acces a lexical variable (declared with my()) outside
its scope. The only kind-of exception are closures ... subroutines
defines inside the variable's scope and thus able to access it later.
But that's not what you want.
Jenda
=========== Jenda@Krynicky.cz == http://Jenda.Krynicky.cz ==========
There is a reason for living. There must be. I've seen it somewhere.
It's just that in the mess on my table ... and in my brain
I can't find it.
--- me
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