Pros/cons of my/our sought

Mur has asked for the wisdom of the Perl Monks concerning the following question:

There may be MTOWTDI, but what criteria might cause me to pick one over t'other?

{
 my $num = 0;
 sub count_it {
    $num++;
 }
 sub print_it {
    print $num, "\n";
 }
}
[download]

vs.

sub count_it {
   our $num ||= 0;
   $num++;
}
sub print_it {
   our $num ||= 0;
   print $num, "\n";
}
[download]

Which is "better", under what circumstances?

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Comment on Pros/cons of my/our sought Select or Download Code

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Re: Pros/cons of my/our sought by broquaint (Abbot) on May 14, 2002 at 18:31 UTC
`our()` pros creates package variables with ease visible across the scope of the file cons clutters package namespace visible across the scope of the file globals don't scale `my()` pros creates lexical variables which are safer and don't dirty a package's namespace my()ed variables behave well and will destroy/untie/evaporate when they fall out of scope you can do funky things like closures with my()ed variables cons my()ed vars don't stick around long enough to pick up the cheque ;-) Basically `our()` is designed for getting around using `vars`, whereas the use of `my()` encourages safer programming and goes hand in hand with `strict` which is a much praised practice in the monastery. HTH `_________ broquaint`	[reply]
Re: Pros/cons of my/our sought by cjf (Parson) on May 14, 2002 at 18:12 UTC
See 'our' is not 'my'.	[reply]
Re: Pros/cons of my/our sought by blakem (Monsignor) on May 15, 2002 at 08:00 UTC
my is probably what you want, since it creates a lexical variable that can't be tampered with outside of the block its delcared in. Take a look at this code: #!/usr/bin/perl -wT use strict; # use an our-variable.... sub count_our { our $num \|\|= 0; $num++; } sub print_our { our $num \|\|= 0; print $num, "\n"; } # use a my-variable.... { my $num = 0; sub count_my { $num++; } sub print_my { print $num, "\n"; } } # thousand lines of code here # $num is common enough that we use it somewhere else as well my $num = 10; our $num = 10; # thousand lines of code here # did we mess up the 'my' variable? count_my(); print "My count: "; print_my(); # how about the 'our' variable? count_our(); print "Our count: "; print_our(); [download] Notice that the our-variable gets fubared somewhere in the middle of this script. The my-variable is truly encapsulated and can't be modified except by count_my() and print_my(). -Blake	[reply] [d/l]
(jeffa) Re: Pros/cons of my/our sought by jeffa (Bishop) on May 14, 2002 at 19:58 UTC
Check out (jeffa) 3Re: Whether to use local() for yet even more explaination. For an interesting use for our, read samtregar's Re: (jeffa) 3Re: seeking different ways to slice a 2-d array. Thanks again Sam. :) jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply]
Re: Pros/cons of my/our sought by Anonymous Monk on May 14, 2002 at 18:31 UTC
In your second usage consider what might happen as your program becomes more complex and you or someone else adds more subroutines. Without carefully checking the entire codebase for existing our globals you may easily stomp on the global $num in another routine or block.	[reply]