How to freeze/thaw anonymous subroutines?

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

Hi all!

I've got a question that sets my head spinning. I've been asked about the possibility of freeze/thawing a scalar that's a subroutine reference. Can anyone make any suggestions? Will the B perl compiler module be of any use to me?

For example, say I have the following:

my $a = sub { print "Hello!\n" };

I want to be able to store $a to a file, read it back from that file, and be still able to call it. Data::Dumper returns: $VAR1 = sub { "DUMMY" }, which obviously doesn't survive the round-trip.

So to reiterate, I'd like to know what freeze and thaw would look like in the following scenario:

  my $a = sub { print "Hello\n" };
  freeze( $a, "frozen.sub.file" );
  $a = undef;
  thaw( $a, "frozen.sub.file" );
  $a->(); # calls $a, printing "Hello\n"
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Any and all assistance is greatly appreciated!

- m.

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Re: How to freeze/thaw anonymous subroutines?
by crazyinsomniac (Prior) on Jun 26, 2002 at 08:36 UTC

from perldoc Storable

The Storable package brings persistence to your Perl data structures containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be conveniently stored to disk and retrieved at a later time.

perl -MStorable=freeze -e freeze(sub{1})

Can't store CODE items at blib\lib\Storable.pm (autosplit into blib\li
+b\auto\Storable\_freeze.al) li
ne 282, at - line 3
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B::Deparse

It'd be easies to comment your code consistently like

sub WHATEVER { # WHATEVER STARTS HERE

} # WHATEVER ENDS HERE
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Re: How to freeze/thaw anonymous subroutines?
by rob_au (Abbot) on Jun 26, 2002 at 09:21 UTC

Juerd

crazyinsomniac

this thread

The summary of this thread is that B::Deparse can be used for only a limited subset of code references, due to the private scope of variables and closure bindings. In particular, this problem was demonstrated with code in this post by merlyn.

In light of this, it may be prudent to re-evaluate this requirement for serialised code references and shift this "external code" to child modules or external scripts.

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Re: How to freeze/thaw anonymous subroutines?
by Juerd (Abbot) on Jun 26, 2002 at 08:24 UTC

Maybe you can use B::Deparse, but there is no "good" way to do this.

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