[Mastering-perl] Perl Contexts & Symbol Tables and Typeglobs

[brian d foy]

On 1/2/07, Florian Merges <fmerges at cpan.org> wrote:

> Ch. Symbol Tables and Typeglobs

> =========================

>

> Section: Package and lexical variables

> --------------------------------------------------------

>

> $n and $global should be declared with 'our'


I've never really been fond of our as a way to declare variables. It's
useful to bring a package variable into play when a lexical of the
same name is in scope, but otherwise is just a trick to get around use
strict. If I really want to make something global, I prefer to list
them all in 'use vars' :)

However, for those examples I'm specifically avoiding our() until
later so I don't hit the reader with everything at once.



> The first code example, instead of using the 'foreach' idiom, I would suggest:



> print join "\n", keys %main::;


I could do that, I guess, but it really doesn't add anything to the
discussion. In the later example where I check the definedness on the
var types for each identifier I would have to go back to foreach(), so
I might as use it in the same way in the preceding examples.






>

>

> Section: Package and lexical variables -> Full package specification

> --------------------------------------------------------------------------------------------------

>

> Last example output should be:

>

> In the naked block, our $global is --> I'm the global version

> In lexical, my $global is --> I'm in the lexical version

> The package version is still --> I'm the global version

> In lexical(): I'm the global version

>

> Section: The symbol table

> --------------------------------------

>

> The first code example, instead of using the 'foreach' idiom, I would

> suggest:

>

> print join "\n", keys %main::;

>

> Section: The symbol table -> Naming anonymous subroutines

> -----------------------------------------------------------------------------------------

>

> ..., and then using that function to created two anonymous subroutines.

>

> ==> what?

>

>

> Kind regards,

>

> Florian

>

>

>

>

>

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>



-- 
brian d foy <brian.d.foy at gmail.com>
http://www.pair.com/~comdog/