amw1 has asked for the wisdom of the Perl Monks concerning the following question:

Is it possible to have variables inside of a coderef evaluated before Storable stores them? i.e. these chunks of code

store_create.pl 
use Storable;
use strict;

my $x = 10;

my $coderef = sub {
    print "\nx is: $x\n";
};

$Storable::Deparse = 1;
Storable::nstore($coderef, 'frozen_ref');

[download]
store_retrieve.pl 
use Storable;
use strict;

$Storable::Eval = 1;
my $coderef = Storable::retrieve('frozen_ref');
&$coderef();

[download]
I think what I'm looking for is a way to store a lexical closure but I'm not 100% sure of the terminology.
The store_retrieve.pl executes the code but $x is undef, I'm looking for a way to have it be 10.

Replies are listed 'Best First'.
Re: coderefs and storable
by kvale (Monsignor) on Mar 12, 2004 at 18:53 UTC
    Here is an example of a closure in your case: 
    my $coderef;
{
   my $x = 10;

   $coderef = sub {
       print "\nx is: $x\n";
   };
}

    [download]

    -Mark

[reply]
[d/l]
      Alternatively ... 
      my $coderef = do {
    my $x = 10;
    sub { print "\nx is : $x\n"; };
};

      [download]

      ------
      We are the carpenters and bricklayers of the Information Age.

      Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.

[reply]
[d/l]
        ultimately what I'm trying to do is to insert an action (as a serialized code ref) into a database to be run at a later time. $x will need to change for different instances of the coderef. Something like. . . . (pseudo code) 
        sub RemoveThing
{
  my $thingid = shift();

  # QueueAction serializes it's first argument
  QueueAction(\&Handlers::thing_remove())
}

package Handlers;

sub thing_remove
{
   database foo to remove $thingid;
}

        [download]
        I know I can make QueueAction take an argument list for passing to the serialized subroutine. Just trying to avoid it.
[reply]
[d/l]
Re: coderefs and storable
by diotalevi (Canon) on Mar 12, 2004 at 19:15 UTC
    You'll be wanting lisp. Paul Graham wrote something doing just this. Closures are not serializable. Code refs, maybe.
[reply]
      I'm hearing that more and more. My boss is quite fond of lisp and in talking to him I'm becoming quite fond of it. I need to spend some time and learn the language.
[reply]

Back to Seekers of Perl Wisdom