Mine or Ours

logie17 has asked for the wisdom of the Perl Monks concerning the following question:

Could someone please give a good example as to why one would use to use our $varname vs. my $varname. According to the Perldoc:

"our" has the same scoping rules as "my", but does not necessarily cre
+ate a variable.
[download]

Could someone explain this to me and supply a good working example?

Thanks in advance,

s;;5776?12321=10609$d=9409:12100$xx;;s;(\d*);push @_,$1;eg;map{print chr(sqrt($_))."\n"} @_;

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Re: Mine or Ours by BrowserUk (Patriarch) on Jan 20, 2007 at 18:43 UTC
Seven Useful Uses of Local might help. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]
Re: Mine or Ours by jdporter (Paladin) on Jan 20, 2007 at 19:07 UTC
Did you think to check out the Tutorials section of the site? If so, you should have found 'our' is not 'my'. Other tutorials in the Variables and Scoping category might also be helpful to you. A word spoken in Mind will reach its own level, in the objective world, by its own weight	[reply]
Re: Mine or Ours by shmem (Chancellor) on Jan 21, 2007 at 00:03 UTC
Apart from the links already provided, my/local, space/time might be helpful; our is different to both. Apart from our, you have also `use vars LIST`. They are similar, but different. Both create package globals, but variables created with our are also ~~file~~ lexical scoped. If you have multiple packages (namespaces) in one file, a variable declared with our is visible in all those packages but file scoped for alien packages, because a symbol table slot only exists for the package the variable was declared in: `use strict; package foo; our $quux = "Howdy, world!\n"; # dump symbol table print "foo: $_ => $foo::{$_}\n" for keys %foo::; package bar; # dump symbol table print "bar: $_ => $bar::{$_}\n" for keys %bar::; print $quux; __END__ foo: quux => foo::quux Howdy, world!` [download] There you have the "does not necessarily create a variable" part - no variable is created in package bar. The variable `$quux` is shared between both packages - they would say "it's our $quux" if they could speak. Same applies for variables declared with our in different files. Having a file as `# file include.pl use strict; our $me; sub japh { print $me,"\n"; }` [download] to be included in a main script `#!/usr/bin/perl use strict; our $me = "Just another perl hacker"; require "include.pl"; japh();` [download] running the main script will output `Just another perl hacker` [download] The `$me` variable is shared* between the two files. That's what our means ;-) --shmem update: corrected "file scoped" to "lexical scoped". See Re^4: Mine or Ours. _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l] [select]
Re^2: Mine or Ours by gaal (Parson) on Jan 21, 2007 at 06:53 UTC
`our` isn't file scoped, it's lexically scoped. If you happen to put your `our` at the top level, it behaves similarly to file scope. (But the storage allocated is in some package's symbol table and can be accessed from outside the file, for example with its fully qualified name.) The syntactic range ("range" being a tentative disambiguation term I'm inventing here instead of the overloaded "scope") of `our` and `my` are identical.	[reply] [d/l] [select]
Re^3: Mine or Ours by shmem (Chancellor) on Jan 21, 2007 at 09:24 UTC
Similar or identical? what would be the difference, if similar? `{ our $foo = "bar"; my $quux = "foo"; } print "'$quux'\n"; print "'$foo'\n"; __END__ '' 'bar'` [download] our and my behave pretty different here, which is why I said "file scoped", which may be wrong. The "syntactical range" of my and our are identical in so far as my variables also are visible within their scope throughout different packages (which scope is different to that of our variables). our creates a package global, which is visible througout the entire file, even crossing packages. So file or lexical scope is pretty much the same. If "file scoped" means "only visible in that file", then no, our is not file scoped. Sorry for any confusion caused. --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l]
Re^4: Mine or Ours by gaal (Parson) on Jan 21, 2007 at 09:44 UTC
Re^5: Mine or Ours by shmem (Chancellor) on Jan 21, 2007 at 10:08 UTC
Re^2: Mine or Ours by Herkum (Parson) on Jan 21, 2007 at 03:10 UTC
I did not know that our was also file scoped. I never use it which probably why it has never been a problem but you never know when you may come across something. For a simple question, still get to learn something... :)	[reply]

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